Zoom lens and imaging device

Abstract

An object of the present invention is to provide a standard zoom lens system that has high optical performance while reducing the weight of the focus group and the vibration reduction group, and an imaging device equipped with the zoom lens system. [Solution] To solve the above problems, the zoom lens of the present invention has a front group having negative refractive power overall and a rear group having positive refractive power overall, with the object side positioned on the widest air space at the widest end and the image side positioned on the rear group, and varies magnification from the wide-angle end to the telephoto end by changing the air space between the lens groups. It includes a focus group F located within the rear group and moving along the optical axis when focusing from infinity to a close object, and an image stabilization group VC located closer to the object than the focus group F and movable in a direction approximately perpendicular to the optical axis, satisfying certain conditions. An imaging device is also provided with the zoom lens.

Description

Technical Field

[0001] The present invention relates to a zoom lens and an imaging device, and particularly to a zoom lens and an imaging device suitable for an imaging device using a solid-state imaging device (such as a CCD or a CMOS) such as a digital still camera or a digital video camera.

Background Art

[0002] Conventionally, imaging devices using solid-state imaging devices such as digital still cameras, digital video cameras, single-lens reflex cameras, and mirrorless cameras have become widespread. In these imaging devices, an imaging lens called a standard zoom lens is widely used. A standard zoom lens generally refers to a zoom lens that includes a focal length of 50 mm in the zoom range in terms of 35 mm equivalent.

[0003] For example, Patent Document 1 proposes a standard zoom lens composed of, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. In this zoom lens, the second lens group is moved toward the object side to focus on the subject.

Prior Art Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the zoom lens disclosed in Patent Document 1, the second lens group responsible for the main variable magnification action is used as the focus group. The second lens group has a large number of lens elements and is heavy compared to other lens groups. Therefore, it is difficult to perform rapid autofocus. Also, since the second lens group is heavy, the drive mechanism for moving the second lens group during focusing also becomes large. As a result, there has been a problem of causing an increase in size and weight of the entire lens unit including the lens barrel.

[0006] In recent years, at least one lens included in the optical system is used as an anti-shake group, and when image blur occurs due to camera shake or the like during imaging, the image is shifted by moving the anti-shake group in a direction substantially perpendicular to the optical axis. When such an anti-shake mechanism is incorporated into a zoom lens, it is necessary to arrange a drive mechanism for moving the anti-shake group in a direction substantially perpendicular to the optical axis within the lens barrel. Therefore, in order to reduce the size and weight of the entire zoom lens unit, the miniaturization and weight reduction of the anti-shake group, as well as the positional relationship between the focus group and the anti-shake group, become important.

[0007] Therefore, an object of the present invention is to provide a small-sized standard zoom lens with high optical performance and an imaging device equipped with the zoom lens while achieving weight reduction of the focus group and the anti-shake group.

Means for Solving the Problems

[0008] In order to solve the above problems, in the zoom lens according to the present invention, when the lens group arranged on the object side is defined as the front group and the lens group arranged on the image side is defined as the rear group with the widest air interval at the wide-angle end as a boundary, the front group has a negative refractive power as a whole, the rear group has a positive refractive power as a whole, and variable magnification is performed from the wide-angle end to the telephoto end by changing the air interval between the lens groups so as to decrease at least the air interval between the front group and the rear group, a focus group arranged within the rear group and moving in the optical axis direction when focusing from infinity to a nearby object, an anti-shake group arranged on the object side of the focus group and movable in a direction substantially perpendicular to the optical axis, and includes The rear group has at least one lens Lrn with a negative refractive power on the object side of the focus group, The focus group has at least one lens Ln with a negative refractive power, and is characterized by satisfying the following conditions. (1) 3.80 < Cr1f / fw (8) 1.84 < NdLrn < 2.10 (12) 51.0 < νdLn < 98.0 (14) 0.01 < Crrf / ft ≦ 0.433 However, Cr1f: The radius of curvature of the object-side surface of the zoom lens fw: The focal length of the zoom lens at the wide-angle end NdLrn: The refractive index of the lens Lrn at the d-line νdLn: The Abbe number of the lens Ln at the d-line Crrf: The radius of curvature of the object-side surface of the rear group ft: The focal length of the zoom lens at the telephoto end

[0009] In addition, in order to solve the above problems, an imaging device according to the present invention includes the zoom lens according to the present invention, and an image sensor that is disposed on the image side of the zoom lens and converts an optical image formed by the zoom lens into an electrical signal.

Effects of the Invention

[0010] According to the present invention, it is possible to provide a standard zoom lens with high optical performance and an imaging device including the zoom lens while reducing the weight of the focus group.

Brief Description of the Drawings

[0011]

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Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the zoom lens and imaging device according to the present invention will be described. However, the zoom lens and imaging device described below are one aspect of the zoom lens and imaging device according to the present invention, and the zoom lens and imaging device according to the present invention are not limited to the following aspects.

[0013] 1. Zoom lens 1-1. Optical configuration of the zoom lens First, the optical configuration of the zoom lens of this embodiment will be described. In the zoom lens of this embodiment, when the lens group arranged on the object side is defined as the front group and the lens group arranged on the image side is defined as the rear group with the widest air gap at the wide-angle end as the boundary, the front group has a negative refractive power as a whole, and the rear group has a positive refractive power as a whole. When zooming from the wide-angle end to the telephoto end, the air gap between the lens groups is changed so as to decrease at least the air gap between the front group and the rear group. In addition, the zoom lens includes a focus group that moves in the optical axis direction when focusing from infinity to a nearby object, and an anti-vibration group that is arranged on the object side of the focus group and can move in a direction substantially perpendicular to the optical axis, and the focus group is arranged within the rear group.

[0014] In this zoom lens, a retrofocus type power arrangement is adopted, with the front group having a diverging action and the rear group having a converging action, with the widest air space at the wide-angle end as the boundary. Therefore, while suppressing the enlargement of the zoom lens, it becomes easier to widen the angle of view at the wide-angle end. That is, since this zoom lens adopts a power arrangement suitable for a standard zoom lens, it can achieve a wide angle of view at the wide-angle end, ensure a back focus suitable for an interchangeable lens system such as a single-lens reflex camera, and configure the whole to be small. However, this zoom lens shall have a half angle of view (ω) at the wide-angle end greater than 24° while including a focal length of 50 mm in the zoom range in terms of 35 mm equivalent.

[0015] In this zoom lens, a negative refractive power is arranged in the front group and a positive refractive power is arranged in the rear group. When zooming from the wide-angle end to the telephoto end, the air space between the front group and the rear group is decreased. Although the incident light angle with respect to the front group varies with zooming, the variation in the incident light angle with respect to the rear group is small. Therefore, by arranging the focus group in the rear group, the angle-of-view variation during focusing can be suppressed. Accordingly, since the angle-of-view variation is small even when wobbling is performed, a zoom lens suitable for video imaging can be realized.

[0016] Furthermore, in this zoom lens, the diameter of the incident light beam with respect to the rear group is smaller than the diameter of the incident light beam with respect to the front group. Therefore, by arranging the focus group in the rear group, the miniaturization and weight reduction of the focus group can be achieved as compared with the case where the focus group is arranged in the front group.

[0017] Furthermore, the zoom lens includes an anti-shake group that is movable in a direction substantially perpendicular to the optical axis on the object side of the focus group. When vibration is transmitted to the imaging device during imaging due to so-called camera shake or the like and image blur occurs, the image can be shifted by moving the anti-shake group in a direction substantially perpendicular to the optical axis. That is, image blur correction can be performed. In the zoom lens, the focus group is arranged on the image side of the zoom lens. Therefore, by arranging the anti-shake group on the object side of the focus group, a drive mechanism for moving the focus group in the optical axis direction (including mechanical members, motors, electrical components, etc., hereinafter referred to as the "focus drive mechanism") and a drive mechanism for moving the anti-shake group in a direction substantially perpendicular to the optical axis (including mechanical members, magnets, coils, electrical components, etc., hereinafter referred to as the "anti-shake drive mechanism") can be compactly arranged in the lens barrel. In addition, various wirings become easier, and the entire zoom lens unit including the lens barrel of the zoom lens can be downsized. On the other hand, when the anti-shake group is arranged on the image side of the focus group, in order to compactly arrange the focus drive mechanism and the anti-shake drive mechanism in the lens barrel, there are restrictions on the arrangement of the anti-shake group, and it becomes difficult to realize the required optical performance. In addition, it becomes difficult to downsize the zoom lens unit. However, the configurations of the focus drive mechanism and the anti-shake drive mechanism are not particularly limited. Hereinafter, the optical configuration of the zoom lens will be described in more detail.

[0018] (1) The widest air gap at the wide-angle end First, the air gap between the front group and the rear group will be described. The zoom lens is composed of a plurality of lens groups. When zooming from the wide-angle end to the telephoto end, the air gap between each lens group changes. The size of the air gap between each lens group changes depending on the zoom position of the zoom lens. Therefore, in the present invention, among the air gaps between the lens groups constituting the zoom lens, the widest air gap at the wide-angle end of the zoom lens is referred to as the "widest air gap at the wide-angle end".

[0019] In addition, the air interval between lens groups that changes according to the zoom position of the zoom lens is referred to as a variable interval. At this time, the "widest air interval at the wide-angle end" refers to the maximum variable interval among the variable intervals between the lens group arranged on the object side and the lens group arranged on the image side in the zoom lens, and does not include the air interval (back focus) between the lens group arranged on the image side and the imaging surface in the zoom lens. Then, with the "widest air interval at the wide-angle end" as a boundary, one or a plurality of lens groups arranged on the object side are referred to as the front group, and one or a plurality of lens groups arranged on the image side are referred to as the rear group.

[0020] (2) Front group The front group is a general term for one or a plurality of lens groups arranged on the object side of the above-mentioned "widest air interval at the wide-angle end". Since the front group has a negative refractive power as a whole, the front group has at least one lens group having a negative refractive power.

[0021] Among the lens groups having a negative refractive power included in the front group, the lens group having the largest negative refractive power is referred to as the negative lens group n. As long as the front group has this negative lens group n and has a negative refractive power as a whole, the other lens group configurations are not particularly limited. For example, the front group may have two or more lens groups having a negative refractive power, or may have one or more lens groups having a positive refractive power.

[0022] However, from the viewpoint of being effective in increasing the aperture of the zoom lens, it is preferable that the front group includes a lens group having a positive refractive power on the object side. And in the front group, arranging a lens group having a negative refractive power on the image side of the lens group having a positive refractive power is also effective in increasing the magnification of the zoom lens.

[0023] (3) Rear group The rear group is a general term for one or more lens groups arranged on the image side with respect to the "widest air interval at the wide-angle end" described above. Since the rear group has a positive refractive power as a whole, the rear group has at least one lens group having a positive refractive power. The rear group includes the above focus group, and as long as it has a positive refractive power as a whole, the configuration of other lens groups is not particularly limited. For example, it may have two or more lens groups having a positive refractive power, or may have one or more lens groups having a negative refractive power. Also, in order to reduce the size of the zoom lens, it is preferable to arrange a lens group having a positive refractive power on the most object side of the rear group from the viewpoints of high magnification and large aperture, but this point is not particularly limited either.

[0024] The rear group preferably has at least one lens on the image side of the focus group. By arranging at least one lens on the image side of the focus group, it becomes easy to correct aberration variations accompanying the movement of the focus group at the time of focusing on the image side of the focus group. At this time, the refractive power of the lens may be positive, but the lens preferably has at least one lens surface Sr having a negative refractive power. By arranging a lens having at least one lens surface Sr on the image side of the focus group, it becomes easy to reduce field curvature.

[0025] Also, the rear group preferably has at least one lens Lrn having a negative refractive power on the object side of the focus group. By arranging a lens Lrn having a negative refractive power on the object side of the focus group, field curvature can be reduced, and it becomes easy to reduce chromatic aberration. At the same time, aberrations generated in the focus group can be reduced by the lens Lrn. Therefore, the amount of aberration generation to be corrected at the time of focusing is small, and it becomes easy to realize a zoom lens having high optical performance over the entire focusing range.

[0026] (4) Focus group The focus group is either one of the lens groups constituting the rear group or a part thereof. The configuration of the focus group is not particularly limited, but for the reasons described later, it is preferably composed of one single lens unit. Here, the single lens unit refers to a lens unit such as a single lens or a cemented lens in which a plurality of single lenses are integrated without an air gap therebetween. That is, even if the single lens unit has a plurality of optical surfaces, only the object-side surface and the image-side surface are in contact with air, and the other surfaces are not in contact with air. In this specification, the single lens may be either a spherical lens or an aspherical lens. The aspherical lens also includes a so-called composite aspherical lens having an aspherical film attached to its surface.

[0027] When the focus group is composed of the above one single lens unit, the focus group does not include an air gap. Therefore, compared with a configuration in which a plurality of single lenses are arranged with an air gap therebetween, the zoom lens can reduce the size and weight of the focus group. As a result, the size of various mechanical members, motors, electrical components, etc. constituting the focus drive mechanism can be reduced, and the weight of the focus drive mechanism can be reduced.

[0028] Also, compared with a configuration in which a plurality of single lenses are arranged with an air gap therebetween, by configuring the focus group from the above one single lens unit, various manufacturing errors such as eccentricity errors and errors in the air gap between single lenses can be reduced. Therefore, the deterioration of optical performance due to manufacturing errors can be reduced, and the variation in performance for each product can be reduced. Accordingly, a zoom lens with high optical performance can be manufactured with high yield.

[0029] Furthermore, it is preferable that the focus group has a negative refractive power. That is, it is preferable that the combined refractive power of the single lens unit is negative. By having the focus group have a negative refractive power, it is possible to cancel out the field curvature and distortion aberration generated in the front group having a negative refractive power with the focus group. Therefore, a zoom lens with higher optical performance can be obtained.

[0030] Here, the focus group only needs to be composed of one single lens unit, and it may be composed of one single lens, or it may be composed of one cemented lens in which a plurality of single lenses are cemented and unitized. In any case, the above-described series of effects can be obtained. Compared with the case where the focus group is composed of a cemented lens, using only one single lens can reduce the weight and size of the focus group.

[0031] On the other hand, when the focus group is composed of a cemented lens, compared with the case where the focus group is composed of only one single lens, the optical performance can be improved. For example, by configuring the focus group from a cemented lens including a lens (lens Lp) having a positive refractive power and a lens (lens Ln) having a negative refractive power, the occurrence of chromatic aberration when focusing on a nearby subject can be suppressed, and a zoom lens with higher optical performance can be realized.

[0032] When the focus group is composed of the above cemented lens, the order of arrangement of the lens Lp and the lens Ln is not particularly limited, but it is preferable that the cemented lens is cemented in the order of the lens Lp and the lens Ln from the object side. As described above, the focus group is arranged in the rear group. In this case, when compared with the axial ray, the off-axis ray passes through a more peripheral part of the single lens unit constituting the focus group. This is because in order to correct the longitudinal chromatic aberration better, it is preferable to arrange a lens having a negative refractive power on the image side.

[0033] (5) Aperture stop In this zoom lens, the arrangement of the aperture stop is not particularly limited. However, the aperture stop referred to here is the aperture stop that defines the light beam diameter of the zoom lens, that is, the aperture stop that defines the Fno of the zoom lens.

[0034] However, it is preferable to arrange the aperture stop on the object side of the rear group or within the rear group in order to obtain good optical performance throughout the entire focusing range. As described above, the variation in the diameter of the incident light beam with respect to the rear group is small. Therefore, by arranging the aperture stop on the object side of the rear group or within the rear group, it is possible to suppress the aberration variation during focusing.

[0035] (6) Vibration-proof group The vibration-proof group is arranged on the object side of the focus group. Therefore, as described above, it becomes easy to compactly arrange each drive mechanism within the lens barrel, and various wirings also become easier, enabling miniaturization of the zoom lens unit.

[0036] In this zoom lens, the vibration-proof group may be arranged on the object side of the focus group. Therefore, the vibration-proof group may be arranged in the front group or in the rear group. However, as described above, in this zoom lens, the diameter of the incident light beam with respect to the rear group is smaller than the diameter of the incident light beam with respect to the front group. Therefore, by arranging the vibration-proof group in the rear group, it is possible to reduce the size and weight of the vibration-proof group as compared with the case where the vibration-proof group is arranged in the front group.

[0037] Also, it is more preferable that the vibration-proof group is arranged on the image side of the aperture stop. Between the aperture stop and the focus group, the variation in the height of the light ray during zooming is small, and the aberration variation during zooming is also small. Therefore, by arranging the vibration-proof group between the aperture stop and the focus group, it is possible to reduce the aberration variation during image blur correction (during vibration-proof). Thus, it is possible to realize a high-performance zoom lens with small aberration variation even during vibration-proof throughout the entire zoom range.

[0038] The number of lenses constituting the anti-vibration group may be one or a plurality. In terms of suppressing aberration variation during anti-vibration, it is preferable that the number of lenses constituting the anti-vibration group is a plurality. In particular, the anti-vibration group is preferably composed of at least one lens Lvcn having a negative refractive power and at least one lens Lvcp having a positive refractive power, which can suppress the occurrence of chromatic aberration during anti-vibration and realize a zoom lens with higher optical performance.

[0039] Also, it is preferable that the anti-vibration group is composed of one lens Lvcn having a negative refractive power and one lens Lvcp having a positive refractive power. By configuring the anti-vibration group with two lenses of positive and negative, it is possible to suppress the occurrence of chromatic aberration during anti-vibration and reduce the size and weight of the anti-vibration group. As a result, it is possible to reduce the size and weight of the anti-vibration drive mechanism, and to reduce the size and weight of the entire zoom lens unit.

[0040] Here, it is preferable that the anti-vibration group is composed of a cemented lens in which the lens Lvcn and the lens Lvcp are cemented. In this case, the anti-vibration group does not include an air gap. Therefore, for example, compared with a configuration in which the lens Lvcn and the lens Lvcp are arranged with an air gap therebetween, the size and weight of the anti-vibration group can be reduced in the zoom lens.

[0041] Also, compared with a configuration in which the anti-vibration group is arranged with the lens Lvcn and the lens Lvcp with an air gap therebetween, by configuring the anti-vibration group from a single lens unit in which the lens Lvcn and the lens Lvcp are cemented, various manufacturing errors such as eccentricity error and error of the air gap between lenses can be reduced. Therefore, it is possible to reduce the deterioration of optical performance caused by manufacturing errors and reduce the variation in performance for each product. Therefore, a zoom lens with high optical performance can be manufactured with good yield.

[0042] Furthermore, it is preferable that the anti-vibration group has at least one aspherical surface. By having at least one aspherical surface in the anti-vibration group, the amount of coma aberration generated during anti-vibration can be suppressed. Therefore, an anti-vibration group with a small number of lens elements and a small amount of aberration generated can be configured, so that the anti-vibration group can be miniaturized and lightened. A zoom lens with high optical performance can be realized, the anti-vibration group can be miniaturized and lightened, and the anti-vibration drive mechanism can be miniaturized and lightened.

[0043] In addition, it is preferable that the aspherical surface has an aspherical shape in which the refractive power is weaker than the refractive power obtained from its paraxial curvature. By arranging an aspherical surface of such a shape in the anti-vibration group, it becomes easier to correct coma aberration and partial defocus during anti-vibration, and a zoom lens with higher optical performance can be realized. Note that the partial defocus during anti-vibration refers to the aberration that appears in a state where when the anti-vibration group is eccentric during anti-vibration, the actual image plane is inclined in the direction in which the anti-vibration group is eccentric with respect to the ideal image plane.

[0044] (7) Lens group configuration The number of lens groups constituting the zoom lens is not particularly limited. For example, it may be composed of a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power, and is a zoom lens having a five-group configuration in which the lens groups after the third lens group are the rear groups, or it may be composed of a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power, and is a zoom lens having a four-group configuration in which the lens groups after the second lens group are the rear groups, or it may be composed of a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a negative refractive power, and a sixth lens group having a positive refractive power, and is a zoom lens having a six-group configuration in which the lens groups after the third lens group are the rear groups. Various lens group configurations can be adopted. As long as it has a configuration including a front group having a negative refractive power on the object side and a rear group having a positive refractive power on the image side with the widest air space at the wide-angle end as the boundary, the specific lens group configuration of the zoom lens is not particularly limited.

[0045] 1-2. Operation (1) Operation during zooming In the zoom lens, when zooming from the wide-angle end to the telephoto end, the air space between the lens groups is changed so that at least the air space between the front group and the rear group decreases.

[0046] Here, when the front group and / or the rear group includes a plurality of lens groups, it is assumed that the air space between each lens group also changes during zooming. When zooming from the wide-angle end to the telephoto end, it is only necessary that at least the air space between the front group and the rear group decreases, and the increase or decrease of the air space between the other lens groups is not particularly limited. Also, when zooming, all the lens groups constituting the zoom lens may be moved in the optical axis direction, or some of the lens groups may be fixed in the optical axis direction and the remaining lens groups may be moved in the optical axis direction. The presence or absence of movement and the direction of movement of each individual lens group are not particularly limited.

[0047] Here, when zooming from the wide-angle end to the telephoto end, if the first lens group, which is the lens group arranged closest to the object side in the zoom lens, is moved toward the object side, the overall optical length of the zoom lens at the wide-angle end can be shortened. In this case, the lens barrel has a nested structure in which the inner barrel part is accommodated in the outer barrel part so that it can be extended. For example, when zooming from the wide-angle end to the telephoto end, the inner barrel part is extended to move the first lens group toward the object side, and when zooming from the telephoto end to the wide-angle end, the inner barrel part is accommodated in the outer barrel part. In this way, the length of the lens barrel in the wide-angle end state can be shortened, and the zoom lens unit can be made smaller.

[0048] (2) Operation during focusing In the zoom lens, when focusing from infinity to a nearby object, the focus group arranged in the rear group moves in the optical axis direction. The direction of movement of the focus group during focusing is not particularly limited. For example, it is preferably moved toward the image side when focusing from infinity to a nearby object.

[0049] Here, when a negative refractive power is arranged in the front group arranged on the object side, a positive refractive power is arranged in the rear group arranged on the image side, and the focus group is arranged in the rear group, the amount of axial chromatic aberration and the amount of spherical aberration generated during imaging of a nearby subject are less at the wide-angle end than at the telephoto end. Therefore, even if the shortest imaging distance at the wide-angle end is made shorter than the shortest imaging distance at the telephoto end, the amount of each aberration generated at the wide-angle end is small. Therefore, by making the shortest imaging distance at the wide-angle end shorter than the shortest imaging distance at the telephoto end, the imaging angle of view can be appropriately selected according to the distance to the subject and the size of the subject, and the imaging scene that can be imaged by the zoom lens can be expanded. However, the shortest imaging distance (shortest shooting distance) refers to the shortest distance from the imaging plane to the subject.

[0050] Note that when focusing, in addition to the focus group composed of the above-described cemented lens, another lens group or a part of a lens group may also be moved. That is, focusing may be performed by a floating method. In an imaging lens adopting a retrofocus type power arrangement, when the floating method is adopted, aberration correction at the time of focusing becomes easy. Therefore, in order to realize a zoom lens with high optical performance, it is preferable to perform focusing by the floating method.

[0051] However, in the floating method, since a plurality of lens groups are moved at the time of focusing, the configuration of the focus drive mechanism becomes complicated. Therefore, in order to reduce the size and weight of the zoom lens, it is preferable to move only the focus group composed of the above-described cemented lens at the time of focusing, rather than the floating method. That is, it is preferable that the zoom lens does not include a lens group that moves on the optical axis at the time of focusing, other than the above-described focus group.

[0052] Note that in the present invention, even when focusing is performed by the floating method, the focus group may satisfy the configurations and conditions described in this specification. That is, the other lens group or a part of a lens group that moves together with the focus group at the time of focusing is not particularly limited.

[0053] 1-2. Conditional Expression In the zoom lens, it is preferable to adopt the above-described configuration and satisfy at least one or more of the conditional expressions described below.

[0054] 1-2-1. Conditional Expression (1) (1) 3.80 < Cr1f / fw However, Cr1f: The radius of curvature of the most object-side surface of the zoom lens fw: The focal length of the zoom lens at the wide-angle end

[0055] Conditional expression (1) is an equation for defining the ratio of the radius of curvature of the object-side surface of the zoom lens to the focal length of the zoom lens at the wide-angle end. The fact that the value of conditional expression (1) is positive means that the object-side surface of the zoom lens is flat or convex on the object side. By satisfying conditional expression (1), the radius of curvature of the object-side surface of the zoom lens falls within an appropriate range with respect to the focal length of the zoom lens at the wide-angle end, and it is possible to balance and correct distortion and field curvature.

[0056] On the other hand, when the numerical value of conditional expression (1) is equal to or less than the lower limit value, the radius of curvature of the object-side surface of the zoom lens becomes too small with respect to the focal length of the zoom lens at the wide-angle end, overcorrection of distortion occurs, and correction of field curvature becomes difficult, which is not preferable.

[0057] In order to obtain these effects, it is more preferable that the lower limit value of conditional expression (1) is 4.00, further preferably 4.20, still more preferably 4.50, even more preferably 4.80, even further preferably 5.10, and most preferably 6.50. Also, the upper limit value of conditional expression (1) is not particularly limited, but if an upper limit value is provided, it is preferably 100.00, more preferably 50.00, and still more preferably 40.00.

[0058] 1-2-2. Conditional expression (2) (2) 0.50 < (-ffw + Dfrw) / FBw < 2.00 However, ffw: Composite focal length of the front group at the wide-angle end Dfrw: Distance on the optical axis between the image-side surface of the front group and the object-side surface of the rear group at the wide-angle end FBw: Air-equivalent length from the image-side surface of the zoom lens to the imaging surface at the wide-angle end

[0059] Conditional expression (2) is an expression for defining the ratio between the focal point of the light beam incident on the rear group and the focal point of the light beam emitted from the rear group at the wide-angle end. In conditional expression (2), the numerator represents the distance on the optical axis from the focal point of the light beam incident on the rear group to the most object-side surface of the rear group. The denominator is the so-called back focus, which represents the distance on the optical axis between the focal point of the light beam emitted from the rear group and the most image-side surface of the rear group. By satisfying conditional expression (2), it is possible to miniaturize the zoom lens while ensuring an appropriate back focus suitable for the interchangeable lens system. At this time, the most object-side surface of the front group refers to the lens surface arranged on the most object side in the front group, and the most image-side surface of the rear group refers to the lens surface arranged on the most image side in the rear group.

[0060] On the other hand, when the numerical value of conditional expression (2) becomes equal to or greater than the upper limit value, the back focus at the wide-angle end becomes shorter. Therefore, it becomes difficult to ensure a back focus suitable for the interchangeable lens system. Also, the fact that the numerical value of conditional expression (2) is equal to or greater than the upper limit value means that the focal point of the light beam incident on the rear group is far. That is, since the focal point of the light beam incident on the rear group is on the object side and the overall optical length at the wide-angle end becomes long, it becomes difficult to miniaturize the zoom lens. From these facts, it is preferable that the numerical value of conditional expression (2) is less than the upper limit value.

[0061] On the other hand, when the numerical value of conditional expression (2) becomes equal to or less than the lower limit value, the back focus at the wide-angle end becomes long, so it becomes easier to ensure a back focus suitable for the interchangeable lens system. However, if the back focus becomes too long, the overall optical length at the wide-angle end becomes long. Therefore, also in this case, it becomes difficult to miniaturize the zoom lens. From these facts, it is preferable that the numerical value of conditional expression (2) is greater than the lower limit value.

[0062] In order to obtain these effects, the lower limit value of conditional expression (2) is preferably 0.60, more preferably 0.70, still more preferably 0.80, even more preferably 0.90, still even more preferably 1.05, and yet even more preferably 1.15. Also, the upper limit value of conditional expression (2) is preferably 1.95, and more preferably 1.92.

[0063] 1-2-3. Conditional Expression (3) In the zoom lens, it is preferably as described above that the anti-vibration group includes at least one lens Lvcn having a negative refractive power and at least one lens Lvcp having a positive refractive power. At this time, it is more preferable to satisfy the following conditions.

[0064] (3) 22.00 < 1 / |(1 / νdLvcn) - (1 / νdLvcp)| < 70.00 However, νdLvcn: Abbe number of lens Lvcn at d-line νdLvcp: Abbe number of lens Lvcp at d-line

[0065] Conditional expression (3) is an expression for defining the difference in Abbe number between the lens Lvcn and the lens Lvcp when the anti-vibration group includes the lens Lvcn and the lens Lvcp. When conditional expression (3) is satisfied, the balance between chromatic aberration correction and lens material cost is improved, and it is possible to realize a zoom lens with high optical performance and less chromatic aberration during anti-vibration while suppressing excessive cost increase.

[0066] On the other hand, when the value of conditional expression (3) is equal to or greater than the upper limit value, chromatic aberration correction becomes insufficient, and it becomes difficult to correct magnification chromatic aberration during anti-vibration, which is not preferable. On the other hand, when the value of conditional expression (3) is equal to or less than the lower limit value, chromatic aberration is overcorrected, and in this case too, it becomes difficult to correct magnification chromatic aberration during anti-vibration, which is not preferable. Furthermore, lens materials for which the value of conditional expression (3) is equal to or less than the lower limit value are high refractive index materials and are expensive. Therefore, from the perspective of cost, it is not preferable for the value of conditional expression (3) to be equal to or less than the lower limit value.

[0067] In order to obtain these effects, the lower limit value of conditional expression (3) is more preferably 22.50, even more preferably 23.00, still more preferably 23.50, yet more preferably 24.00, and even yet more preferably 24.20. Also, the upper limit value of conditional expression (3) is more preferably 60.00, even more preferably 55.00, still more preferably 50.00, and yet more preferably 47.00.

[0068] Here, if the anti-vibration group includes at least one of the above-described lens Lvcn and the above-described lens Lvcp, the above-described effects can be obtained. At this time, the anti-vibration group may include a lens that does not satisfy conditional expression (3), but it is preferable in terms of chromatic aberration and cost that all the lenses included in the anti-vibration group satisfy conditional expression (3). It is more preferable in terms of chromatic aberration and cost that the anti-vibration group is composed of two lenses, one lens Lvcn and one lens Lvcp.

[0069] 1-2-4. Conditional Expression (4) (4) 0.50 < |(1-βvct)×βvctr| < 6.00 However, βvct: Lateral magnification at infinity focus of the anti-vibration group at the telephoto end βvctr: Combined lateral magnification at infinity focus of all lenses arranged on the image side of the anti-vibration group at the telephoto end

[0070] Conditional expression (4) is an expression for defining the shake correction coefficient of the anti-vibration group. Here, the shake correction coefficient represents the amount of movement of the imaging surface when the anti-vibration group moves by a unit amount. When conditional expression (4) is satisfied, the amount of movement of the anti-vibration group during anti-shake can be within an appropriate range, realizing high-precision and rapid image shake correction, and facilitating miniaturization of the zoom lens.

[0071] On the other hand, when the numerical value of conditional expression (4) is equal to or less than the lower limit value, the blur correction coefficient of the vibration-proof group becomes too small. Therefore, the movement amount of the vibration-proof group during vibration-proof becomes large, and it is necessary to increase the outer diameter of the lens barrel to secure a space in which the vibration-proof group can move. In addition, when the movement amount of the vibration-proof group increases, the size of the vibration-proof drive mechanism also increases. For these reasons, it becomes difficult to miniaturize the zoom lens, which is not preferable. Further, when the numerical value of conditional expression (4) is equal to or greater than the upper limit value, the blur correction coefficient of the vibration-proof group becomes too large. Therefore, the movement amount of the vibration-proof group during image blur correction becomes too small, which requires high-precision position control and is not preferable.

[0072] In order to obtain these effects, the lower limit value of conditional expression (4) is more preferably 0.60, further preferably 0.70, still more preferably 0.85, even more preferably 1.00, and even further preferably 1.10. Also, the upper limit value of conditional expression (4) is more preferably 5.00, further preferably 4.10, still more preferably 3.00, even more preferably 2.30, and even further preferably 2.20.

[0073] 1-2-5. Conditional expression (5) (5) 0.00 < (Crff + Crfr) / (Crff - Crfr) < 5.00 However, Crff: Curvature radius of the object-side surface of the focus group Crfr: Curvature radius of the image-side surface of the focus group

[0074] The above conditional expression (5) is an expression for defining the shapes of the nearest object side surface and the nearest image side surface of the focus group. The nearest object side surface of the focus group refers to the object side surface of the lens that is arranged on the most object side among the lenses constituting the focus group. Similarly, the nearest image side surface of the focus group refers to the image side surface of the lens that is arranged on the most image side among the lenses constituting the focus group. By setting the shapes of the nearest object side surface and the nearest image side surface of the focus group to the shapes defined by the above conditional expression (5), it becomes possible to perform good correction of spherical aberration, reduce aberration fluctuations when focusing on a nearby subject, and realize a zoom lens with high optical performance across the entire focusing range.

[0075] In order to obtain these effects, the lower limit value of the conditional expression (5) is more preferably 0.05, even more preferably 0.08, still more preferably 0.10, and yet more preferably 0.15. Also, the upper limit value of the conditional expression (5) is more preferably 4.50, even more preferably 4.00, and still more preferably 3.00.

[0076] 1-2-6. Conditional Expression (6) (6) 1.20 < |{1 - (βft × βft)} × βftr × βftr| < 15.00 However, βft: Lateral magnification at infinity focus of the focus group at the telephoto end βftr: Combined lateral magnification at infinity focus of all lenses arranged on the image side of the focus group in telephoto

[0077] The conditional expression (6) is an expression for defining the focus sensitivity of the focus group. Here, the focus sensitivity represents the amount of movement of the imaging surface when the focus group moves by a unit amount. When the conditional expression (6) is satisfied, the amount of movement of the focus group when focusing from an infinite object to a nearby object can be set within an appropriate range, realizing rapid autofocus and facilitating miniaturization of the zoom lens.

[0078] On the other hand, when the numerical value of the conditional expression (6) is equal to or less than the lower limit value, the focus sensitivity of the focus group becomes too small. Therefore, when focusing from an infinite object to a close object, the movement amount of the focus group increases, and the overall optical length becomes longer. As a result, it becomes difficult to miniaturize the zoom lens, which is not preferable. Also, when the numerical value of the conditional expression (6) is equal to or greater than the upper limit value, the focus sensitivity of the focus group becomes too large. Therefore, the movement amount of the focus group for correcting the misalignment of the focus position becomes too small, requiring high-precision position control, which is not preferable.

[0079] In order to obtain these effects, the lower limit value of the conditional expression (6) is more preferably 1.50, further preferably 2.00, still more preferably 2.50, even more preferably 3.00, and even further preferably 3.60. Also, the upper limit value of the conditional expression (6) is more preferably 14.00, further preferably 13.00, and still more preferably 12.00.

[0080] (6-1) |βft|>1 Here, the absolute value of "βft" in the conditional expression (6) is preferably greater than 1. As described above, "βft" refers to the lateral magnification at infinity focus of the focus group at the telephoto end. The focus group is included in the rear group. By giving a lateral magnification greater than 1 to the lens group (focus group) included in the rear group, the overall optical length direction and the diameter direction of the zoom lens can be miniaturized.

[0081] 1-2-7. Conditional expression (7) In the zoom lens, it is preferably to have at least one lens surface Sr having a negative refractive power on the image side with respect to the focus group as described above. At this time, it is more preferable to satisfy the following conditional expression.

[0082] (7)-0.400 <|fw×tanωw| / (fsr-FBw)< -0.002 However, ωw: The half field angle of the outermost chief ray of the zoom lens at the wide-angle end fsr: Focal length of lens surface Sr

[0083] Conditional expression (7) is an expression that pseudo-represents the ratio between the converging point of lens surface Sr and the image height of the outermost chief ray on the imaging surface. Here, the chief ray refers to the ray passing through the center of the aperture stop. By arranging a lens surface Sr that satisfies conditional expression (7) on the image side of the focus group, the field curvature can be well corrected by the lens surface Sr. Therefore, it becomes easier to further improve the performance of the zoom lens.

[0084] On the other hand, when the numerical value of conditional expression (7) becomes equal to or greater than the upper limit value, the negative refractive power of lens surface Sr becomes too small. In this case, the field curvature tilts too much to the under side, making it difficult to improve the performance of the zoom lens, so this is not preferable. On the contrary, when the numerical value of conditional expression (7) becomes equal to or less than the lower limit value, the negative refractive power of lens surface Sr becomes too large. In this case, the correction of the Petzval sum is insufficient, making it difficult to improve the performance of the zoom lens, which is not preferable. Also, the lens surface Sr may have two or more surfaces. At this time, it is only necessary for any one surface to satisfy conditional expression (7). More preferably, when all lens surfaces Sr satisfy conditional expression (7), it becomes easy to realize performance improvement.

[0085] In order to obtain these effects, it is more preferable that the upper limit value of conditional expression (7) is -0.004, even more preferably -0.006, still more preferably -0.008, even still more preferably -0.010, and yet even still more preferably -0.012. Also, it is more preferable that the lower limit value of conditional expression (7) is -0.350, even more preferably -0.300, still more preferably -0.250, even still more preferably -0.230, and yet even still more preferably -0.220.

[0086] 1-2-8. Conditional expression (8) In this zoom lens, it is preferable as described above that the rear group has at least one lens Lrn having a negative refractive power on the object side with respect to the focus group. At this time, it is preferable to satisfy the following conditions.

[0087] (8) 1.84 < NdLrn < 2.10 However, NdLrn: Refractive index of lens Lrn at the d line

[0088] The conditional expression (8) is an expression that defines the refractive index of lens Lrn at the d line. Here, the rear group has a positive refractive power as a whole. Therefore, in order to correct the Petzval sum well, it is necessary to arrange a lens having a negative refractive power made of a high-refractive-index optical material in the rear group. The optical material that satisfies the conditional expression (8) has a good balance when considering the correction of the Petzval sum and the optical material cost. Therefore, by having the rear group have a lens Lrn that satisfies the conditional expression (8) on the object side of the focus group, it is possible to realize a zoom lens with high optical performance while suppressing excessive cost increase.

[0089] On the other hand, when the value of the conditional expression (8) is below the lower limit value, the refractive index of the above lens Lrn at the d line is small, and the correction of the Petzval sum cannot be sufficiently performed, which is not preferable. On the other hand, when the value of the conditional expression (8) is above the upper limit value, the refractive index of the above lens Lrn at the d line becomes large, which is preferable for correcting the Petzval sum. However, an optical material with a large refractive index at the d line is generally more expensive than an optical material with a small refractive index at the d line. When an optical material with a refractive index at the d line above the upper limit value is used, although there is an effect on the correction of the Petzval sum, the effect is small considering the cost-effectiveness. Therefore, it is not preferable from a cost perspective that the value of the conditional expression (8) is above the upper limit value.

[0090] In order to obtain these effects, the lower limit value of conditional expression (8) is more preferably 1.860, even more preferably 1.870, and still more preferably 1.880. Also, the upper limit value of conditional expression (8) is more preferably 2.070, even more preferably 2.010, and still more preferably 1.960.

[0091] 1-2-9. Conditional Expression (9) In the zoom lens, it is preferable as described above that the rear group has a lens Lrn having at least one negative refractive power lens on the object side relative to the focus group. At this time, it is preferable to satisfy the following conditions.

[0092] (9) -0.015 < ΔPgF < 0.022 However, ΔPgF: Deviation from the reference line of the partial dispersion ratio, when in a coordinate system with the partial dispersion ratio on the vertical axis and the Abbe number νd for the d-line on the horizontal axis, using as the reference line a straight line passing through the coordinates of optical material C7 with a partial dispersion ratio of 0.5393 and νd of 60.49 and the coordinates of optical material F2 with a partial dispersion ratio of 0.5829 and νd of 36.30

[0093] Here, assuming that the refractive indices of the glass for the g-line (435.8 nm), F-line (486.1 nm), d-line (587.6 nm), and C-line (656.3 nm) are Ng, NF, Nd, and NC respectively, the Abbe number (νd) and the partial dispersion ratio (PgF) can be expressed as follows. νd = (Nd - 1) / (NF - NC) PgF = (Ng - NF) / (NF - NC)

[0094] Conditional expression (9) is an expression for defining the anomalous dispersibility of lens Lrn. Here, the rear group has a positive refractive power as a whole. In order to correct chromatic aberration in a lens group having a positive refractive power, it is common to combine a negative lens made of a high-dispersion optical material and a positive lens made of a low-dispersion optical material. However, the dispersion characteristics of the high-dispersion optical material with respect to wavelength are quadratic, and the dispersion characteristics of the low-dispersion optical material with respect to wavelength are linear. Therefore, when a negative lens made of a high-dispersion optical material and a positive lens made of a low-dispersion optical material are combined, although chromatic aberration can be made zero at a certain wavelength, chromatic aberration remains at other wavelengths, and chromatic aberration cannot be corrected over the entire use wavelength range.

[0095] Therefore, by combining a lens Lrn made of an optical material with low anomalous dispersibility that satisfies the above conditional expression (9) and having a negative refractive power, and a positive lens made of an optical material with high anomalous dispersibility to be described below, for example, it becomes possible to correct chromatic aberration over the entire use wavelength range. Thus, by arranging the lens Lrn having a negative refractive power that satisfies the conditional expression (9) on the object side of the focus group, it becomes possible to realize a zoom lens with high optical performance and good chromatic aberration correction over the entire use wavelength range. Note that it is more preferable for the lens Lrn to satisfy the above conditional expression (8) and the conditional expression (9) for better correction of chromatic aberration.

[0096] In order to obtain these effects, the lower limit value of the conditional expression (9) is more preferably -0.012, and even more preferably -0.010. Also, the upper limit value of the conditional expression (9) is more preferably 0.014, even more preferably 0.013, and still more preferably 0.012.

[0097] Here, in the zoom lens, it is preferable that the rear group has a lens Lrn that satisfies the conditional expression (9) on the object side of the focus group and a lens Lrp having a positive refractive power that satisfies the following conditional expression (9-1).

[0098] (9-1) 0.009 < ΔPgFp < 0.060 However, ΔPgFp: The deviation from the reference line of the partial dispersion ratio when, in a coordinate system with the partial dispersion ratio on the vertical axis and the Abbe number νd with respect to the d-line on the horizontal axis, a straight line passing through the coordinates of the optical material C7 with a partial dispersion ratio of 0.5393 and νd of 60.49 and the coordinates of the optical material F2 with a partial dispersion ratio of 0.5829 and νd of 36.30 is used as the reference line

[0099] Optical materials that satisfy the conditional expression (9-1) have a high degree of anomalous dispersion, and the dispersion characteristics with respect to wavelength are quadratic. Therefore, by arranging a lens Lrp having a positive refractive power that satisfies the conditional expression (9-1) together with the lens Lrn that satisfies the conditional expression (9) in the rear group, a zoom lens with good chromatic aberration can be realized over the entire wavelength range used.

[0100] 1-2-10. Conditional Expression (10) In the zoom lens, the front group has at least one lens group having a negative refractive power. When the lens group having the largest negative refractive power in the front group is defined as the negative lens group n, it is preferable to satisfy the following conditions.

[0101] (10) -2.00 < fn / fw < -0.55 However,[[]] fn: Focal length of the negative lens group n fw: Focal length of the zoom lens at the wide-angle end

[0102] The conditional expression (10) is an expression that defines the ratio of the focal length of the negative lens group n included in the front group to the focal length of the zoom lens at the wide-angle end. By satisfying the conditional expression (10), it becomes easy to widen the angle of view at the wide-angle end while suppressing the increase in size of the zoom lens. In addition, correction of field curvature, coma aberration, distortion aberration, etc. can be performed with a small number of lenses, and a small-sized zoom lens with high optical performance can be realized.

[0103] On the other hand, when the numerical value of the conditional expression (10) is equal to or less than the lower limit value, the refractive power of the negative lens group n having the largest refractive power among those included in the front group becomes smaller with respect to the focal length at the wide-angle end of the zoom lens. Therefore, the effect of expanding the angle of view by the negative lens group n disposed in the front group becomes smaller. In that case, in order to widen the angle of view at the wide-angle end, it is necessary to increase the outer diameter of the so-called front lens, making it difficult to reduce the size of the zoom lens. On the other hand, when the numerical value of the conditional expression (10) is equal to or greater than the upper limit value, the refractive power of the negative lens group n having the largest refractive power among those included in the front group becomes larger with respect to the focal length at the wide-angle end of the zoom lens. Therefore, it becomes difficult to correct various aberrations such as field curvature, coma aberration, and distortion aberration. As a result, in order to realize a zoom lens with high optical performance, it is necessary to increase the number of lens elements for aberration correction, making it difficult to reduce the size of the zoom lens.

[0104] In order to obtain these effects, the lower limit value of the conditional expression (10) is more preferably -1.90, even more preferably -1.80, and still more preferably -1.60. Also, the upper limit value of the conditional expression (10) is more preferably -0.58, even more preferably -0.62, and still more preferably -0.68.

[0105] 1-2-11. Conditional Expression (11) (11) -0.70 < ff / ft < -0.05 However, ff: Focal length of the focus group ft: Focal length of the zoom lens at the telephoto end

[0106] The above conditional expression (11) is an expression for defining the ratio of the focal length of the focus group to the focal length of the zoom lens at the telephoto end. When the conditional expression (11) is satisfied, the occurrence of axial chromatic aberration, spherical aberration, field curvature, etc. can be suppressed when focusing on a nearby subject, and a zoom lens with high optical performance can be realized over the entire focusing range. Further, when the conditional expression (11) is satisfied, since the refractive power of the focus group is within an appropriate range, the focus sensitivity can be set within an appropriate range. When the focus sensitivity is within an appropriate range, the movement amount of the focus group when focusing from an infinite object to a nearby object can be set within an appropriate range, enabling rapid autofocus and facilitating miniaturization of the zoom lens.

[0107] On the other hand, when the value of the conditional expression (11) is below the lower limit value, the focal length of the focus group becomes larger than the focal length of the zoom lens at the telephoto end. That is, the refractive power of the focus group becomes too small. In this case, since the focus sensitivity of the focus group becomes too low, the movement amount of the focus group when focusing on a nearby subject becomes large. Therefore, it is necessary to secure an air gap for moving the focus group, leading to an increase in the overall optical length of the zoom lens, which is not preferable. On the other hand, when the value of the conditional expression (11) is above the upper limit value, the focal length of the focus group becomes smaller than the focal length of the zoom lens at the telephoto end. That is, the refractive power of the focus group becomes too large. In this case, since axial chromatic aberration, spherical aberration, and field curvature when focusing on a nearby subject become large, it becomes difficult to maintain high optical performance over the entire focusing range, which is not preferable. Further, in this case, the focus sensitivity of the focus group becomes too high. When the focus sensitivity becomes too high, high-precision position control is required to correct the misalignment of the focus position, which is not preferable.

[0108] In order to obtain these effects, the lower limit value of the conditional expression (11) is more preferably -0.65, even more preferably -0.60, still more preferably -0.55, and yet more preferably -0.45. Also, the upper limit value of the conditional expression (11) is more preferably -0.08, even more preferably -0.10, and still more preferably -0.12.

[0109] 1-2-12. Conditional Expression (12) In the zoom lens, the focus group preferably has a lens Ln having at least one negative refractive power and satisfies the following conditions.

[0110] (12) 45.0 < νdLn < 98.0 However, νdLn: Abbe number of the lens Ln at the d line

[0111] The above conditional expression (12) is an expression for defining the Abbe number of the lens Ln having a negative refractive power included in the focus group. When the conditional expression (12) is satisfied, chromatic aberration correction becomes good, and it becomes easy to realize a zoom lens with high optical performance. Also, the optical materials that satisfy the conditional expression (12) are mostly optical materials with relatively small specific gravity, which is also effective for reducing the weight of the focus group.

[0112] On the other hand, when the value of the conditional expression (12) is below the lower limit value, the chromatic dispersion of the above lens Ln becomes large, and it becomes difficult to correct the axial chromatic aberration when focusing on an object at a finite distance, which is not preferable. On the other hand, when the value of the conditional expression (12) is above the upper limit value, the chromatic dispersion of the above lens Ln constituting the focus group becomes small, which is preferable for correcting chromatic aberration. However, optical materials with a large Abbe number are more expensive than optical materials with a small Abbe number. When an optical material with an Abbe number above the upper limit value is used, although there is an effect on chromatic aberration correction, considering the cost-effectiveness, the effect is small. Therefore, it is not preferable from a cost perspective that the value of the conditional expression (12) is above the upper limit value.

[0113] In order to obtain these effects, the lower limit value of conditional expression (12) is more preferably 45.5, further preferably 46.0, still more preferably 47.0, even more preferably 49.0, and yet even more preferably 51.0. Also, the upper limit value of conditional expression (12) is more preferably 82.0, further preferably 76.0, still more preferably 68.0, even more preferably 65.0, and yet even more preferably 62.0.

[0114] 1-2-13. Conditional expression (13) In the zoom lens, it is preferable as described above that the first lens group moves toward the object side when zooming from the wide-angle end to the telephoto end. In this case, it is preferable to satisfy the following conditional expression (13).

[0115] (13) 0.01 < |X1| / ft < 0.65 However, X1: The amount of movement when the first lens group moves from the most image-side position to the most object-side position where the first lens group can be located during zooming from the wide-angle end to the telephoto end ft: The focal length of the zoom lens at the telephoto end

[0116] The above conditional expression (13) is an expression for defining the amount of movement of the first lens group toward the object side when zooming from the wide-angle end to the telephoto end. When conditional expression (13) is satisfied, the refractive power of the first lens group is appropriate, and the amount of movement during zooming is within an appropriate range. Therefore, while ensuring a predetermined zoom ratio, the overall optical length of the zoom lens at the wide-angle end can be shortened, and the zoom lens can be miniaturized.

[0117] On the other hand, when the numerical value of the conditional expression (13) is equal to or less than the lower limit value, the movement amount of the first lens group during zooming becomes small. In this case, in order to ensure a predetermined zoom ratio, it is necessary to increase the refractive power of each lens group. When the refractive power of each lens group is increased, a large number of lens elements are required for aberration correction such as axial chromatic aberration and spherical aberration, making it difficult to miniaturize the zoom lens. Further, when the numerical value of the conditional expression (13) is equal to or greater than the upper limit value, the movement amount of the first lens group during zooming becomes large. In this case, when the lens barrel has a nested structure in which the inner barrel portion is housed in the outer barrel portion, if the lens barrel length is designed in accordance with the overall optical length at the wide-angle end, it becomes necessary to double the inner barrel portion and house it in the outer barrel portion, etc., the structure of the lens barrel becomes complicated and the outer diameter of the lens barrel also increases, which is not preferable.

[0118] However, the "movement amount when the first lens group moves from the most image-side position to the most object-side position where the first lens group can be located while zooming from the wide-angle end to the telephoto end" is equal to the "distance (difference) on the optical axis between the most image-side position where the first lens group can be located and the most object-side position where the first lens group can be located while zooming from the wide-angle end to the telephoto end". Therefore, "X1" can be rephrased as the "distance on the optical axis between the most image-side position where the first lens group can be located and the most object-side position where the first lens group can be located while zooming from the wide-angle end to the telephoto end". For example, when the first lens group moves toward the object side while drawing a convex locus toward the image side when zooming from the wide-angle end to the telephoto end, the distance between the position of the apex of the convex locus (the most image-side position) drawn by the first lens group during zooming and the position where the first lens group is most on the object side at the wide-angle end or the telephoto end (the most object-side position) is X1. Note that the movement locus of the first lens group may be convex toward the image side, convex toward the object side, or may draw an S shape, and is not particularly limited. Of course, the movement locus of the first lens group may be linear.

[0119] In order to obtain these effects, the lower limit of conditional expression (13) is more preferably 0.05, even more preferably 0.10, still more preferably 0.15, and yet even more preferably 0.20. Also, the upper limit of conditional expression (13) is more preferably 0.60, even more preferably 0.55, still more preferably 0.48, and yet even more preferably 0.46.

[0120] 1-2-14. Conditional Expression (14) (14) 0.01 < Crrf / ft However, Crrf: Radius of curvature of the most object-side surface of the rear group ft: Focal length of the zoom lens at the telephoto end

[0121] The above conditional expression (14) is an expression for defining the ratio between the radius of curvature of the most object-side surface of the rear group and the focal length of the zoom lens at the telephoto end. The fact that the value of conditional expression (14) is positive means that the most object-side surface of the rear group is a flat surface or a convex surface on the object side. When conditional expression (14) is satisfied, the radius of curvature of the most object-side surface of the rear group falls within an appropriate range with respect to the focal length of the zoom lens at the telephoto end, and the correction balance between spherical aberration and coma aberration becomes good.

[0122] In order to obtain these effects, the lower limit of conditional expression (14) is more preferably 0.03, even more preferably 0.06, still more preferably 0.09, and yet even more preferably 0.10. Also, although the upper limit of conditional expression (14) is not particularly limited, if an upper limit is provided, it is preferably 500.00, more preferably 50.00, even more preferably 25.00, and still more preferably 12.00.

[0123] 1-2-15. Conditional Expression (15) (15) 0.10 < ffft / ft < 1.00 However, ffft: Combined focal length of all lenses arranged on the object side of the focus group at the telephoto end ft: Focal length of the zoom lens at the telephoto end

[0124] Conditional expression (15) is an expression for defining the ratio between the combined focal length of all lenses arranged on the object side with respect to the focus group and the focal length at the telephoto end of the zoom lens. When conditional expression (15) is satisfied, the combined lateral magnification of all lens groups arranged on the image side with respect to the focus group falls within an appropriate range, ensuring a predetermined zoom ratio and facilitating the realization of a small-sized zoom lens with high optical performance.

[0125] On the other hand, when the numerical value of conditional expression (15) is equal to or less than the lower limit value, the combined focal length of all lenses arranged on the object side with respect to the focus group becomes shorter than the focal length at the telephoto end of the zoom lens. In this case, the combined lateral magnification of all lens groups arranged on the image side with respect to the focus group increases. Therefore, spherical aberration and field curvature increase, making it difficult to realize a small-sized zoom lens with high optical performance, which is not preferable. On the other hand, when the numerical value of conditional expression (15) is equal to or greater than the upper limit value, the combined focal length of all lenses arranged on the object side with respect to the focus group becomes longer than the focal length at the telephoto end of the zoom lens. In this case, the combined lateral magnification of all lens groups arranged on the image side with respect to the focus group decreases. Therefore, in order to ensure a predetermined zoom ratio, it is necessary to increase the moving distance of each lens group during zooming, making it difficult to achieve miniaturization in the optical axis direction, which is not preferable.

[0126] In order to obtain these effects, it is more preferable that the lower limit value of conditional expression (15) is 0.15, even more preferably 0.20, still more preferably 0.25, even still more preferably 0.30, yet even still more preferably 0.36, and most preferably 0.40. Also, it is more preferable that the upper limit value of conditional expression (15) is 0.90, even more preferably 0.80, still more preferably 0.70, and even still more preferably 0.60.

[0127] 1-2-16. Conditional expression (16) When the zoom lens satisfies the following conditions when the lens surface closest to the focus group in the direction in which the focus group moves during focusing from infinity to a close object is defined as the lens surface Lnf.

[0128] (16) 0.015 < Drfrt / ft < 1.000 However, Drfrt: The distance on the optical axis at infinity focus between the focus group at the telephoto end and the above lens surface Lnf ft: The focal length of the zoom lens at the telephoto end

[0129] The conditional expression (16) is an equation for defining the interval (distance on the optical axis) between the focus group and the lens surface Lnf closest to the focus group in the direction in which the focus group moves during focusing from infinity to a close object. By satisfying the conditional expression (16), it is possible to secure an interval for the focus group to move in a predetermined direction during focusing, and it becomes possible to shorten the shortest imaging distance. Also, satisfying the conditional expression (16) is effective in shortening the shortest imaging distance at the wide-angle end.

[0130] On the other hand, when the value of the conditional expression (16) is below the lower limit value, it is not possible to secure an interval for the focus group to move in a predetermined direction during focusing, and it becomes impossible to shorten the shortest imaging distance, which is not preferable. On the other hand, when the value of the conditional expression (16) is above the upper limit value, the overall optical length at the telephoto end becomes long, which is not preferable in terms of miniaturizing the zoom lens.

[0131] Note that the direction in which the focus group moves when focusing from infinity to a close object may be either the object side or the image side. When the direction in which the focus group moves when focusing from infinity to a close object is the object side, the lens surface Lnf is the lens surface closest to the object side of the focus group. When the direction in which the focus group moves when focusing from infinity to a close object is the image side, the lens surface Lnf is the lens surface closest to the image side of the focus group.

[0132] In order to obtain these effects, the lower limit value of the conditional expression (16) is more preferably 0.020, further preferably 0.030, and still more preferably 0.040. Also, the upper limit value of the conditional expression (16) is more preferably 0.800, further preferably 0.600, still more preferably 0.400, even more preferably 0.300, and yet even more preferably 0.250.

[0133] 1-2-17. Conditional Expression (17) (17) -1.50 < fw / ffw < -0.50 However, fw: Focal length of the zoom lens at the wide-angle end ffw: Composite focal length of the front group at the wide-angle end

[0134] The conditional expression (17) is an expression for defining the ratio between the focal length of the zoom lens at the wide-angle end and the composite focal length of the front group at the wide-angle end. By satisfying the conditional expression (17), it becomes easier to realize a zoom lens with high optical performance using a small number of lens elements.

[0135] On the other hand, when the numerical value of conditional expression (17) is equal to or less than the lower limit value, the combined focal length of the front group at the wide-angle end becomes shorter than the focal length of the zoom lens at the wide-angle end, making it difficult to correct aberrations such as field curvature, coma, and distortion. Therefore, in order to realize a zoom lens with high optical performance, it is necessary to increase the number of lens elements for aberration correction. That is, it is impossible to realize a zoom lens with high optical performance with a small number of lens elements, and it becomes difficult to miniaturize the zoom lens, which is not preferable. On the other hand, when the numerical value of conditional expression (17) is equal to or greater than the upper limit value, the combined focal length of the front group at the wide-angle end becomes longer than the distance of the zoom lens at the wide-angle end, so the effect of widening the angle of view by the front group becomes smaller. Therefore, in order to achieve a wider angle of view at the wide-angle end, it is necessary to increase the lens diameter of the front lens, making it difficult to miniaturize the zoom lens, which is not preferable.

[0136] In order to obtain these effects, the lower limit value of conditional expression (17) is more preferably -1.40, even more preferably -1.30, and still more preferably -1.20. Also, the upper limit value of conditional expression (17) is more preferably -0.55, even more preferably -0.60, and still more preferably -0.63.

[0137] 1-2-18. Conditional expression (18) In the zoom lens, it is more preferable to include a lens Lp having a positive refractive power that satisfies the following conditional expression (18).

[0138] (18) 15.0 < νdLp < 35.0 νdLp: Abbe number of the above lens Lp at the d line

[0139] Conditional expression (18) is an expression for defining the Abbe number of the above lens Lp. When conditional expression (18) is satisfied, chromatic aberration can be corrected well, and a zoom lens with high optical performance can be realized.

[0140] On the other hand, when the numerical value of conditional expression (18) is equal to or less than the lower limit value, chromatic aberration becomes overcorrected, and it becomes difficult to correct axial chromatic aberration when focusing on an object at a finite distance, which is not preferable. Furthermore, the optical material with a numerical value of conditional expression (18) equal to or less than the lower limit value is a high refractive index material and is expensive. Therefore, from the perspective of cost, it is not preferable for the numerical value of conditional expression (18) to be equal to or less than the lower limit value. On the other hand, when the numerical value of conditional expression (18) is equal to or greater than the upper limit value, chromatic aberration is undercorrected, which is not preferable.

[0141] In order to obtain these effects, the lower limit value of conditional expression (18) is preferably 18.0, more preferably 22.0. Also, the upper limit value of conditional expression (18) is preferably 34.0, more preferably 33.0, still more preferably 32.0, even more preferably 31.0, and yet even more preferably 30.0.

[0142] Note that a plurality of the above lenses Lp may be included in the zoom lens. However, from the perspective of achieving high performance while maintaining the zoom lens small, it is preferable that only one lens Lp is included in the zoom lens. Also, the arrangement of the above lens Lp is not particularly limited, and it may be arranged in any lens group of the zoom lens. When the above lens Lp is arranged in the rear group, it is preferable because chromatic aberration correction becomes better. Furthermore, it is more preferable that the above lens Lp is arranged in the focus group, and the focus group is preferably composed of a single lens unit including the above lens Lp. By arranging the above lens Lp in the focus group, it becomes easier to correct axial chromatic aberration when focusing on an object at a finite distance.

[0143] According to the above zoom lens, it is possible to provide a standard zoom lens with high optical performance and an imaging device equipped with the zoom lens while reducing the weight of the focus group. In particular, the zoom lens can include a focal length of 50 mm in the zoom range in terms of 35 mm format, and can make the half angle of view (ω) of the zoom lens at the wide-angle end larger than 24°.

[0144] 2. Imaging Device Next, the imaging device according to the present invention will be described. The imaging device according to the present invention is characterized by including the zoom lens according to the present invention and an imaging element provided on the image plane side of the zoom lens for converting the optical image formed by the zoom lens into an electrical signal.

[0145] Here, the imaging element etc. are not particularly limited, and solid-state imaging elements such as CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors can also be used. The imaging device according to the present invention is suitable for imaging devices using these solid-state imaging elements such as digital cameras and video cameras. Further, the imaging device may be a lens-fixed imaging device in which the lens is fixed to the housing, or of course, may be an interchangeable-lens imaging device such as a single-lens reflex camera or a mirrorless camera. In particular, the zoom lens according to the present invention can ensure a back focus suitable for an interchangeable lens system. Therefore, it is suitable for imaging devices such as single-lens reflex cameras equipped with an optical viewfinder, a phase difference sensor, a reflex mirror for branching light to these, etc.

[0146] The imaging device of the present invention more preferably has an image processing unit that electrically processes the captured image data acquired by the imaging element to change the shape of the captured image, and an image correction data holding unit that holds image correction data, an image correction program, etc. used for processing the captured image data in the image processing unit. When the zoom lens is miniaturized, distortion (aberration) of the shape of the captured image formed on the imaging plane is likely to occur. At that time, it is preferable to previously hold distortion correction data for correcting the distortion of the captured image shape in the image correction data holding unit, and in the above image processing unit, use the distortion correction data held in the image correction data holding unit to correct the distortion of the captured image shape. According to such an imaging device, it is possible to further promote the miniaturization of the zoom lens, obtain a beautiful captured image, and achieve the miniaturization of the entire imaging device.

[0147] Furthermore, in the imaging device according to the present invention, it is preferable that the image correction data holding unit holds magnification chromatic aberration correction data in advance, and the image processing unit uses the magnification chromatic aberration correction data held in the image correction data holding unit to correct the magnification chromatic aberration of the captured image. By correcting the magnification chromatic aberration, that is, the chromatic distortion aberration, by the image processing unit, it becomes possible to reduce the number of lens elements constituting the optical system. Therefore, according to such an imaging device, it is possible to further reduce the size of the zoom lens, obtain a beautiful captured image, and reduce the size of the entire imaging device.

[0148] Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples. The zoom lenses in each of the examples listed below are applicable to imaging devices (optical devices) such as digital cameras, video cameras, and silver halide film cameras. Also, in each lens cross-sectional view, the left side toward the drawing is the object side, and the right side is the imaging surface side. Note that Example 2 and Example 4 are reference examples of the present invention, and Example 1 and Example 3 are examples of the present invention.

Example

[0149] (1) Optical configuration of the zoom lens FIG. 1 is a lens cross-sectional view showing the lens configuration at infinity focus at the wide-angle end of the zoom lens according to Example 1 of the present invention. The zoom lens includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a negative refractive power, and a fifth lens group G5 having a positive refractive power. When focusing from an infinite object to a nearby object, the fourth lens group G4 moves toward the image side along the optical axis. The aperture stop S is disposed on the object side of the third lens group G3. In this example, the front group consists of the first lens group G1 and the second lens group, and the rear group consists of the third lens group G3, the fourth lens group G4, and the fifth lens group G5. The space between the second lens group G2 and the third lens group G3 is the "widest air space at the wide-angle end".

[0150] The configurations of the respective lens groups will be described below. The first lens group G1 is composed of, in order from the object side, a cemented lens in which a negative meniscus lens L1 with a convex object-side surface and a convex lens L2 are cemented together, and a positive meniscus lens L3 with a convex object-side surface.

[0151] The second lens group G2 is composed of, in order from the object side, a negative meniscus lens L4 with a convex object-side surface, a biconcave lens L5, a biconvex lens L6, and a negative meniscus lens L7 with a concave object-side surface. The object-side surface of the negative meniscus lens L4 is an aspherical surface. Also, both surfaces of the negative meniscus lens L7 are aspherical surfaces.

[0152] The third lens group G3 is composed of, in order from the object side, a diaphragm S, a biconvex lens L8, a cemented lens in which a biconcave lens L9 and a biconvex lens L10 are cemented together, a cemented lens in which a biconcave lens L11 and a positive meniscus lens L12 with a convex object-side surface are cemented together, a biconvex lens L13, a cemented lens in which a biconcave lens L14 and a biconvex lens L15 are cemented together, and a biconvex lens L16. The image-side surface of the biconvex lens L8 is an aspherical surface, and the object-side surface of the biconcave lens L11 is an aspherical surface. The biconcave lens L14 is the above-mentioned lens Lrn, and the biconvex lens L15 is the above-mentioned Lrp. The ΔPgF of the biconcave lens L14 is 0.000, and the ΔPgFp of the biconvex lens is 0.0375.

[0153] The fourth lens group G4 is composed of, in order from the object side, a cemented lens in which a positive meniscus lens L17 with a convex image-side surface and a biconcave lens L18 are cemented together. The fourth lens group G4 is composed only of a cemented lens having a negative refractive power. The positive meniscus lens L17 is the above-mentioned lens Lp, and the biconcave lens L18 is the above-mentioned lens Ln.

[0154] The fifth lens group G5 is composed of, in order from the object side, a biconvex lens L19 and a negative meniscus lens L20 with a concave object-side surface. The object-side surface of the negative meniscus lens L20 is the above-mentioned lens surface Sr.

[0155] In the zoom lens of Example 1, when zooming from the wide-angle end to the telephoto end, with respect to the image plane, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the image side, the third lens group G3 moves toward the object side, the fourth lens group G4 moves toward the object side, and the fifth lens group G5 is fixed in the optical axis direction.

[0156] When image blur occurs due to camera shake or the like during imaging, a joining lens in which the biconcave lens L11 and the positive meniscus lens L12 with a convex shape on the object side, which are included in the third lens group G3, are joined is used as an anti-shake group, and the image is shifted by moving the anti-shake group in a direction substantially perpendicular to the optical axis to perform image blur correction. Note that the biconcave lens L11 is the above-mentioned lens Lvcn, and the positive meniscus lens L12 is the above-mentioned lens Lvcp. In addition, the object side surface of the biconcave lens L11 has an aspherical shape such that the refractive power is weaker than the refractive power obtained from the paraxial curvature thereof.

[0157] Also, "IMG" shown in FIG. 1 is an imaging plane, and specifically represents the imaging plane of a solid-state imaging device such as a CCD sensor or a CMOS sensor, or the film surface of a silver halide film. In addition, on the object side of the imaging plane IMG, a parallel plate having substantially no refractive power such as a cover glass CG is provided. Since these points are the same in each lens cross-sectional view shown in other embodiments, the description thereof will be omitted below.

[0158] (2) Numerical Example Next, a numerical example applying the specific numerical values of the zoom lens will be described. Table 1 shows the surface data of the zoom lens. In Table 1, "surface number" is the order of the lens surfaces counted from the object side, "r" is the radius of curvature of the lens surface, "d" is the interval on the optical axis between the lens surfaces, "Nd" is the refractive index with respect to the d-line (wavelength λ = 587.6 nm), "νd" is the Abbe number with respect to the d-line, and "H" indicates the effective radius. Also, "ASP" displayed in the column next to the surface number indicates that the lens surface is an aspherical surface, and "S" represents the aperture stop. Furthermore, in the column of the interval on the optical axis of the lens surface, the notations such as "D5", "D13", etc. mean that the interval on the optical axis of the lens surface is a variable interval that changes during zooming or focusing. Note that all the units of length in each table are "mm", and all the units of the angle of view are "°". Also, "0.0000" of the radius of curvature means a plane surface. Note that the 37th and 38th surfaces in Table 1 are the surface data of the cover glass CG.

[0159] Table 2 is the specification table of the zoom lens. The specification table shows the focal length "f", F-number "Fno", semi-angle of view "ω", image height "Y", and overall optical length "TL" of the zoom lens at infinity focus. However, in Table 2, the values at the wide-angle end, the intermediate focal length state, and the telephoto end are shown in order from the left.

[0160] Table 3 shows the variable intervals on the optical axis of the zoom lens during zooming. In Table 3, the values at infinity focus at the wide-angle end, the intermediate focal length state, and the telephoto end are shown in order from the left. Note that "INF" in the table indicates "∞ (infinity)".

[0161] Table 4 shows the variable intervals on the optical axis of the zoom lens during focusing. Table 4 shows the values when the shooting distances (imaging distances) are 380.00 mm, 400.00 mm, and 400.00 mm at the wide-angle end, the intermediate focal length state, and the telephoto end, respectively. These shooting distances are the shortest imaging distances at each focal length.

[0162] Table 5 shows the focal lengths of each lens group constituting the zoom lens.

[0163] Table 6 shows the aspherical coefficients of each aspherical surface. The said aspherical coefficients are the values when each aspherical shape is defined by the following formula. Also, Table 25 shows the values of each conditional expression (1) to conditional expression (18).

[0164] X(Y)=CY 2 / [1+{1-(1+Κ)·C 2 Y 2} 1 / 2 +A4·Y 4 +A6·Y 6 +A8·Y 8 +A10·Y 10 +A12·Y 12

[0165] However, in Table 6, "E-a" means "×10 -a ". Also, in the above formula, "X" is the displacement amount from the reference plane in the optical axis direction, "C" is the curvature at the surface vertex, "Y" is the height from the optical axis in the direction perpendicular to the optical axis, "Κ" is the conic coefficient, and "An" is the aspherical coefficient of the nth order. Matters regarding these tables are the same in each table shown in other embodiments, so the description will be omitted below.

[0166] [Table 1] Surface number r d Nd vd H 1 164.8841 1.300 2.00069 25.46 31.000 2 106.9087 5.753 1.59282 68.62 30.327 3 2049.3432 0.200 30.056 4 64.4678 5.097 1.59282 68.62 28.300 5 127.7370 D5 27.808 6 ASP 66.2535 1.400 1.87483 41.12 18.405 7 16.5245 8.916 13.821 8 -116.2454 0.800 1.85680 41.86 13.668 9 56.4149 0.200 13.446 10 61.8227 9.135 1.73319 26.22 13.451 11 -25.7135 0.300 13.288 12 ASP -22.4217 1.200 1.70845 51.27 13.182 13 ASP -103.8458 D13 13.108 14 S 0.0000 1.200 8.858 15 44.2087 3.473 1.69350 53.18 12.906 16 ASP -219.2615 1.536 12.944 17 -866.8618 0.800 1.84984 37.32 13.064 18 94.5183 4.469 1.59282 68.62 13.156 19 -44.7943 0.300 13.283 20 ASP -82.7341 0.900 1.74007 48.57 13.312 21 56.0779 2.635 1.84666 23.78 13.331 22 183.1346 2.578 13.356 23 41.0183 5.387 1.74192 48.43 13.775 24 -63.8393 0.200 13.624 25 -539.6209 0.800 1.97110 29.19 13.071 26 20.6597 6.228 1.49700 81.61 12.253 27 -111.4492 0.238 12.264 28 51.0216 5.332 1.61800 63.39 12.159 29 -79.8317 D29 11.800 30 -139.9604 2.500 1.80809 22.76 9.380 31 -31.1560 0.900 1.69350 53.18 9.408 32 ASP 23.4283 D32 9.411 33 246.3353 7.306 1.59282 68.62 14.773 34 -27.2244 0.200 15.146 35 -31.7701 0.800 1.80897 38.14 15.013 36 -80.5852 D36 15.522 37 0.0000 2.000 1.51680 64.20 20.964 38 0.0000 1.000 21.170

[0167] [Table 2] f 24.695 59.995 101.989 Fno 4.119 4.120 4.119 ω 42.156 19.074 11.409 Y 21.633 21.633 21.633 TL 170.000 186.493 207.607

[0168] [Table 3] f 24.695 59.995 101.989 Shooting distance INF INF INF D5 1.000 27.253 51.899 D13 38.860 10.474 1.300 D29 1.242 8.791 13.609 D32 7.117 18.194 19.019 D36 36.700 36.700 36.700

[0169] [Table 4] Shooting distance 380.000 400.000 400.000 D29 1.825 11.176 19.899 D32 6.535 15.809 12.728

[0170] [Table 5] Group Surface Number Focal Length G1 1-5 150.486 G2 6-13 -21.265 G3 14-29 27.830 G4 30-32 -31.313 G5 33-36 114.076

[0171] [Table 6] Surface Number Κ A4 A6 A8 A10 A12 6 0 -1.8735E-06 2.9593E-09 -1.3867E-11 1.5854E-14 -8.4316E-18 12 0 3.0985E-05 -3.0498E-07 2.1696E-09 -7.7151E-12 1.1327E-14 13 0 1.7444E-05 -3.0958E-07 2.0521E-09 -7.3574E-12 1.0024E-14 16 0 1.2534E-05 -6.6064E-09 8.6021E-11 -4.2944E-13 9.2479E-16 20 0 2.1197E-06 -8.9016E-09 6.0935E-11 -2.0221E-13 2.6903E-16 32 0 1.9583E-06 1.0589E-08 -4.3641E-10 3.7956E-12 -1.3630E-14

[0172] Further, FIGS. 2 to 4 respectively show the longitudinal aberration diagrams at the wide-angle end, intermediate focal length state, and telephoto end of the zoom lens according to the first embodiment when focused at infinity. The longitudinal aberration diagrams shown in each figure are, in order from the left side toward the drawing surface, spherical aberration (mm), astigmatism (mm), and distortion (%) respectively. In the diagram representing spherical aberration, the vertical axis represents the ratio to the open F value, the horizontal axis takes defocus, the solid line represents the spherical aberration at the d line (wavelength λ = 587.6 nm), the one-dot chain line represents the spherical aberration at the g line (wavelength λ = 435.8 nm), and the dotted line represents the spherical aberration at the C line (wavelength λ = 656.3 nm). In the diagram representing astigmatism, the vertical axis represents the image height, the horizontal axis takes defocus, the solid line represents the sagittal image plane (ds) with respect to the d line, and the dotted line represents the meridional image plane (dm) with respect to the d line. In the diagram representing distortion, the vertical axis represents the image height, the horizontal axis takes %, and represents distortion. Since the matters regarding these longitudinal aberration diagrams are the same as those in the longitudinal aberration diagrams shown in other embodiments, the description will be omitted below.

[0173] Further, the back focus “fb” at infinity focus at the wide-angle end of the zoom lens is as follows. However, the following values are those without including the cover glass (Nd = 1.5168), and the back focus shown in other embodiments is the same. fb = 39.019 (mm)

Embodiment

[0174] (1) Optical configuration of the zoom lens FIG. 5 is a lens cross-sectional view showing the lens configuration at infinity focus at the wide-angle end of the zoom lens according to the second embodiment of the present invention. The zoom lens is composed of a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power in order from the object side. When focusing from an infinite object to a nearby object, the third lens group G3 moves toward the image side along the optical axis. The aperture stop S is arranged on the most image side of the second lens group G2. In this embodiment, the front group consists of the first lens group G1, and the rear group consists of the second lens group G2, the third lens group G3, and the fourth lens group G4. The space between the first lens group G1 and the second lens group G2 is the “widest air interval at the wide-angle end”.

[0175] The configurations of the respective lens groups will be described below. The first lens group G1 is composed of, in order from the object side, a negative meniscus lens L1 with a convex shape on the object side, a negative meniscus lens L2 with a convex shape on the object side, and a positive meniscus lens L3 with a convex shape on the object side. The image-side surface of the negative meniscus lens L1 is an aspherical surface.

[0176] The second lens group G2 is composed of, in order from the object side, a positive meniscus lens L4 with a convex shape on the object side, a cemented lens in which a negative meniscus lens L5 with a convex shape on the object side and a biconvex lens L6 are cemented together, and an aperture stop S. Both surfaces of the positive meniscus lens L4 are aspherical surfaces. The negative meniscus lens L5 is the above-mentioned lens Lrn. Also, the ΔPgF of the negative meniscus lens L5 is 0.0137.

[0177] The third lens group G3 is composed of, in order from the object side, a cemented lens in which a positive meniscus lens L7 with a convex shape on the image side and a biconcave lens L8 are cemented together. The third lens group G3 is composed only of cemented lenses having a negative refractive power, the positive meniscus lens L7 is the above-mentioned lens Lp, and the biconcave lens L8 is the above-mentioned lens Ln.

[0178] The fourth lens group G4 is composed of, in order from the object side, a positive meniscus lens L9 with a convex shape on the image side, and a cemented lens in which a biconvex lens L10 and a negative meniscus lens L11 with a concave shape on the object side are cemented together. The positive meniscus lens L9 is the above-mentioned lens Lrp. Also, the ΔPgFp of the positive meniscus lens L9 is 0.0375. Also, the object-side surface of the negative meniscus lens L11 is the above-mentioned lens surface Sr.

[0179] In the zoom lens of Example 2, when zooming from the wide-angle end to the telephoto end, with respect to the image plane, the first lens group G1 moves toward the image side, the second lens group G2 moves toward the object side, the third lens group G3 moves toward the object side, and the fourth lens group G4 moves toward the object side.

[0180] When image blur occurs due to camera shake or the like during imaging, the second lens group G2 is used as an anti-shake group, and the image is shifted by moving the anti-shake group in a direction substantially perpendicular to the optical axis to perform image blur correction. The negative meniscus lens L5 is the above-mentioned lens Lvcn, and the positive meniscus lens L4 and the biconvex lens L6 are the above-mentioned lenses Lvcp, respectively. The value (37.770) of the conditional expression (3) in Table 25 is the value when the Abbe number of the biconvex lens L6 is νdLvcp. The value of the conditional expression (3) when the Abbe number of the positive meniscus lens L4 is νdLvcp is 37.890. Further, both surfaces of the positive meniscus lens L4 are aspherical surfaces, and the object side surface has an aspherical shape such that the refractive power becomes weaker than the refractive power obtained from its paraxial curvature.

[0181] (2) Numerical Examples Next, numerical examples applying the specific numerical values of the zoom lens will be described. Table 7 shows the surface data of the zoom lens, and Table 8 shows the lens list of the zoom lens. The 21st surface and the 22nd surface in Table 7 are the surface data of the cover glass CG.

[0182] Table 9 shows the variable interval on the optical axis of the zoom lens during zooming, and Table 10 shows the variable interval on the optical axis of the zoom lens during focusing. Table 10 shows the values when the shooting distances (imaging distances) are 230.00 mm, 250.00 mm, and 250.00 mm at the wide-angle end, the intermediate focal length state, and the telephoto end, respectively. These shooting distances are the shortest imaging distances at each focal length.

[0183] Table 11 shows the focal lengths of each lens group constituting the zoom lens. Table 12 shows the aspherical coefficients of each aspherical surface. Table 25 shows the values of each conditional expression (1) to conditional expression (18).

[0184] In addition, FIGS. 6 to 8 respectively show the longitudinal aberration diagrams at infinity focus at the wide-angle end, the intermediate focal length state, and the telephoto end of the zoom lens of the second embodiment.

[0185] Furthermore, the back focus at infinity focus at the wide-angle end of the zoom lens is as follows. fb = 38.002 (mm)

[0186] [Table 7] Surface number r d Nd vd H 1 664.2203 2.000 1.59201 67.02 19.685 2 ASP 12.4206 9.063 14.659 3 99.0474 1.700 1.83400 37.34 14.679 4 44.9342 0.382 14.536 5 27.4552 4.648 1.76182 26.61 15.052 6 82.1402 D6 14.800 7 ASP 27.5225 4.248 1.61881 63.85 8.001 8 ASP 341.9552 3.733 7.928 9 41.6779 1.000 1.84666 23.78 7.889 10 17.5890 4.766 1.51680 64.20 7.701 11 -20.4065 1.000 7.687 12 S 0.0000 D12 6.788 13 -43.8890 2.597 1.84666 23.78 6.245 14 -13.2199 1.000 1.80420 46.50 6.132 15 29.7835 D15 5.859 16 -217.0738 2.391 1.49700 81.61 5.867 17 -18.3135 0.300 5.905 18 63.0476 2.475 1.49700 81.61 5.747 19 -21.3360 1.000 1.83481 42.72 5.607 20 -161.5834 D20 5.569 21 0.0000 2.000 1.51680 64.20 13.865 22 0.0000 1.000 14.225

[0187] [Table 8] f 18.538 28.896 53.339 Fno 3.605 4.550 5.767 ω 38.587 26.428 14.755 Y 14.200 14.200 14.200 TL 133.849 122.674 120.000

[0188] [Table 9] f 18.538 28.896 53.339 Shooting distance INF INF INF D6 43.626 20.912 1.273 D12 2.450 4.207 10.084 D15 6.788 8.311 7.450 D20 35.683 43.942 55.891

[0189] [Table 10] Shooting distance 230.000 250.000 250.000 D12 3.300 5.738 15.028 D15 5.938 6.780 2.500

[0190] [Table 11] Group Plane number Focal length G1 1-6 -28.619 G2 7-12 23.772 G3 13-15 -22.745 G4 16-20 44.047

[0191] [Table 12] Plane number Κ A4 A6 A8 A10 A12 2 -0.864 9.3680E-06 2.0539E-09 4.6218E-11 7.4937E-15 0.0000E+00 7 0 -1.1011E-05 5.5255E-08 -2.4435E-09 0.0000E+00 0.0000E+00 8 0 2.2843E-05 7.6512E-08 -2.5280E-09 0.0000E+00 0.0000E+00

Example

[0192] (1) Optical configuration of the zoom lens FIG. 9 is a lens cross-sectional view showing the lens configuration at infinity focus at the wide-angle end of the zoom lens according to Example 3 of the present invention. The zoom lens includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a positive refractive power. When focusing from an infinite object to a close object, the fifth lens group G5 moves toward the image side along the optical axis. The aperture stop S is disposed on the most object side of the third lens group G3. In this Example 3, the front group consists of the first lens group G1 and the second lens group G2, and the rear group consists of the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. The space between the second lens group G2 and the third lens group G3 is the "widest air interval at the wide-angle end".

[0193] Hereinafter, the configuration of each lens group will be described. The first lens group G1 includes, in order from the object side, a cemented lens in which a negative meniscus lens L1 with a convex shape on the object side and a convex lens L2 are cemented, and a positive meniscus lens L3 with a convex shape on the object side.

[0194] The second lens group G2 is composed of, in order from the object side, a negative meniscus lens L4 with a convex shape on the object side, a cemented lens in which a biconcave lens L5 and a biconvex lens L6 are cemented, and a negative meniscus lens L7 with a concave shape on the object side. The object-side surface of the negative meniscus lens L4 is an aspherical surface, and both surfaces of the negative meniscus lens L7 are aspherical surfaces.

[0195] The third lens group G3 is composed of, in order from the object side, a diaphragm S, a cemented lens in which three lenses, namely, a negative meniscus lens L8 with a convex shape on the object side, a biconvex lens L9, and a negative meniscus lens L10 with a concave shape on the object side, are cemented, and a biconvex lens L11. The biconvex lens L11 is the lens Lp. Also, the biconvex lens L9 is the lens Lrp. The ΔPgF of the biconvex lens L9 is 0.0194.

[0196] The fourth lens group G4 is composed of, in order from the object side, a cemented lens in which a biconvex lens L12 and a negative meniscus lens L13 with a concave shape on the object side are cemented, a cemented lens in which a biconcave lens L14 and a positive meniscus lens L15 with a convex shape on the image side are cemented, and a biconvex lens L16. The object-side surface of the biconvex lens L12 is an aspherical surface, and both surfaces of the biconvex lens L16 are aspherical surfaces. The biconcave lens L14 is the lens Lrn, and the positive meniscus lens L15 is the lens Lrp. The ΔPgF of the biconcave lens L14 is 0.0036, and the ΔPgFp of the positive meniscus lens L15 is 0.0194.

[0197] The fifth lens group G5 is composed of a biconcave lens L17 with aspherical surfaces on both sides. That is, it is composed of only one single lens having a negative refractive power, and the biconcave lens L17 corresponds to the lens Ln.

[0198] The sixth lens group G6 is composed of a positive meniscus lens L18 with a convex shape on the image side. The object-side surface of the positive meniscus lens L18 is the lens surface Sr.

[0199] In the zoom lens of Embodiment 3, when zooming from the wide-angle end to the telephoto end, with respect to the image plane, the first lens group G1 moves toward the object side, the second lens group G2 moves once toward the image side and then toward the object side, the third lens group G3 moves toward the object side, the fourth lens group G4 moves toward the object side, the fifth lens group G5 moves toward the object side, and the sixth lens group G6 moves once toward the image side and then toward the object side.

[0200] When image blur occurs due to camera shake or the like during imaging, a cemented lens in which the biconvex lens L12 included in the fourth lens group G4 and the negative meniscus lens L13 with a concave shape on the object side are cemented together is used as an anti-shake group, and the image is shifted by moving the anti-shake group in a direction substantially perpendicular to the optical axis to perform image blur correction. Note that the negative meniscus lens L13 is the above-mentioned lens Lvcn, and the biconvex lens L12 is the above-mentioned lens Lvcp. Further, the object-side surface of the biconvex lens L12 has an aspherical shape such that the refractive power is weaker than the refractive power obtained from the paraxial curvature.

[0201] (2) Numerical Examples Next, numerical examples applying the specific numerical values of the zoom lens will be described. Table 13 shows the surface data of the zoom lens, and Table 14 shows the lens list of the zoom lens. Note that the 33rd and 34th surfaces in Table 13 are the surface data of the cover glass CG.

[0202] Table 15 shows the variable interval on the optical axis of the zoom lens during zooming, and Table 16 shows the variable interval on the optical axis of the zoom lens during focusing. Note that Table 16 shows the values when the shooting distances (imaging distances) are 380.00 mm, 400.00 mm, and 400.00 mm at the wide-angle end, the intermediate focal length state, and the telephoto end, respectively. These shooting distances are the shortest imaging distances at each focal length.

[0203] Table 17 shows the focal lengths of the respective lens groups constituting the zoom lens. Table 18 shows the aspherical coefficients of the respective aspherical surfaces. Also, Table 25 shows the values of the respective conditional expressions (1) to (18).

[0204] In addition, FIGS. 10 to 12 respectively show the longitudinal aberration diagrams at infinity focus for the wide-angle end, intermediate focal length state, and telephoto end of the zoom lens of the third embodiment.

[0205] Furthermore, the back focus at infinity focus for the wide-angle end of the zoom lens is as follows. fb = 39.000 (mm)

[0206] [Table 13] Surface number r d Nd vd H 1 323.7548 1.200 1.92119 23.96 31.000 2 162.8221 5.378 1.59282 68.62 30.511 3 -416.6201 0.200 30.309 4 52.5783 6.103 1.59282 68.62 27.700 5 117.8837 D5 27.204 6 ASP 205.3924 0.300 1.51460 49.96 17.800 7 92.8554 1.000 1.72916 54.67 17.549 8 16.2034 9.149 12.854 9 -33.2034 0.800 1.49700 81.61 12.685 10 23.5127 7.798 1.72047 34.71 11.846 11 -53.7846 2.177 11.330 12 ASP -24.1046 1.000 1.85135 40.10 11.000 13 ASP -39.5928 D13 11.078 14 S 0.0000 1.000 7.350 15 33.5262 0.800 2.00100 29.13 11.263 16 22.1705 7.146 1.59282 68.62 11.130 17 -24.7861 0.800 1.80610 40.73 11.214 18 -1553.7806 0.200 11.601 19 45.5555 3.337 1.94595 17.98 11.975 20 -11420.0602 D20 11.917 21 ASP 73.0633 5.117 1.59282 68.62 11.798 22 -34.4056 0.800 1.94595 17.98 11.608 23 -44.4387 0.200 12.500 24 -252.4796 0.800 2.00100 29.13 11.189 25 21.7316 3.716 1.59282 68.62 10.757 26 44.7795 0.200 10.768 27 ASP 32.9204 6.239 1.82098 42.50 10.900 28 ASP -56.3856 D28 10.951 29 ASP -177.3325 1.000 1.59201 67.02 11.450 30 ASP 29.2491 D30 11.132 31 -331.6955 2.594 1.87070 40.73 13.305 32 -82.1148 D32 13.500 33 0.0000 2.000 1.51680 64.20 21.332 34 0.0000 1.000 21.528

[0207] [Table 14] f 25.752 51.482 101.851 Fno 4.123 4.108 4.120 ω 41.307 22.170 11.633 Y 21.633 21.633 21.633 TL 150.364 161.368 203.864

[0208] [Table 15] f 25.752 51.482 101.851 Shooting distance INF INF INF D5 1.000 17.096 42.593 D13 25.849 6.747 1.000 D20 4.201 2.583 1.000 D28 0.997 5.217 1.003 D30 9.581 13.836 20.242 D32 36.681 43.834 65.971

[0209] [Table 16] Shooting distance 380.000 400.000 400.000 D28 1.933 7.951 7.855 D30 8.645 11.101 13.390

[0210] [Table 17] Group Frame number Focal length G1 1 - 5 114.642 G2 6 - 13 -20.988 G3 14 - 20 42.458 G4 21 - 28 45.184 G5 29 - 30 -42.335 G6 31 - 32 124.734

[0211] [Table 18] Frame number Κ A4 A6 A8 A10 A12 6 0 1.2837E-05 -2.1442E-08 5.5949E-11 -1.1996E-13 1.5377E-16 12 0 -8.7531E-06 8.6202E-08 -3.3258E-10 5.1244E-13 -9.3573E-16 13 0 -9.7742E-06 7.6139E-08 -3.0250E-10 3.5047E-13 0.0000E+00 21 0 -5.5002E-06 -1.6789E-08 8.7410E-11 -3.4776E-13 7.7049E-16 27 0 -3.5514E-06 2.9946E-08 3.3719E-10 -1.8317E-12 1.2820E-14 28 0 7.9983E-06 -1.0254E-09 7.7608E-10 -5.3802E-12 2.7034E-14 29 0 -1.2178E-05 1.5756E-07 -1.0359E-09 2.8436E-12 0.0000E+00 30 0 -1.5518E-05 1.5764E-07 -1.0926E-09 2.8672E-12 2.0668E-15

Example

[0212] (1) Optical configuration of the zoom lens FIG. 13 is a lens cross-sectional view showing the lens configuration at infinity focus at the wide-angle end of the zoom lens of Example 4. The zoom lens includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, a fifth lens group G5 having a negative refractive power, and a sixth lens group G6 having a positive refractive power. When focusing from an infinite object to a close object, the fifth lens group G5 moves toward the image side along the optical axis. The aperture stop S is disposed on the most object side of the third lens group G3. In this example, the front group consists of the first lens group G1 and the second lens group G2, and the rear group consists of the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6. The space between the second lens group G2 and the third lens group G3 is the "widest air space at the wide-angle end".

[0213] The configurations of the respective lens groups will be described below. The first lens group G1 is composed of, in order from the object side, a cemented lens in which a negative meniscus lens L1 with a convex object-side surface and a convex lens L2 are cemented together, and a positive meniscus lens L3 with a convex object-side surface.

[0214] The second lens group G2 is composed of, in order from the object side, a negative meniscus lens L4 with a convex object-side surface, a biconcave lens L5, a biconvex lens L6, and a negative meniscus lens L7 with a concave object-side surface. The object-side surface of the negative meniscus lens L4 is an aspherical surface, and both surfaces of the negative meniscus lens L7 are aspherical surfaces.

[0215] The third lens group G3 is composed of, in order from the object side, a diaphragm S, a biconvex lens L8, a cemented lens in which a biconcave lens L9 and a biconvex lens L10 are cemented together, and a cemented lens in which a biconcave lens L11 and a positive meniscus lens L12 with a convex object-side surface are cemented together. The image-side surface of the biconvex lens L8 and the object-side surface of the biconcave lens L11 are aspherical surfaces. The biconvex lens L10 is the above-mentioned lens Lrp. Also, ΔPgFp of the biconvex lens L10 is 0.0194.

[0216] The fourth lens group G4 is composed of, in order from the object side, a biconvex lens L13, a cemented lens in which a biconcave lens L14 and a biconvex lens L15 are cemented together, and a biconvex lens L16. The biconcave lens L14 is the above-mentioned lens Lrn, and the biconvex lens L15 is the above-mentioned lens Lrp. ΔPgF of the biconcave lens L14 is 0.000, and ΔPgFp of the biconvex lens L15 is 0.0375.

[0217] The fifth lens group G5 is composed of, in order from the object side, a cemented lens in which a positive meniscus lens L17 with a convex image-side surface and a biconcave lens L18 are cemented together. The fifth lens group G5 is composed only of a cemented lens having a negative refractive power, the positive meniscus lens L17 is the above-mentioned lens Lp, and the biconcave lens L18 is the above-mentioned lens Ln.

[0218] The sixth lens group G6 is composed of a cemented lens in which a biconvex lens L19 and a negative meniscus lens L20 with a concave shape on the object side are cemented in order from the object side.

[0219] In the zoom lens of Example 4, when zooming from the wide-angle end to the telephoto end, with respect to the image plane, the first lens group G1 moves toward the object side, the second lens group G2 moves toward the image side, the third lens group G3 moves toward the object side, the fourth lens group G4 moves toward the object side, the fifth lens group G5 moves toward the object side, and the sixth lens group G6 is fixed in the optical axis direction.

[0220] When image blur occurs due to camera shake or the like during imaging, a cemented lens in which a biconcave lens L11 included in the third lens group G3 and a positive meniscus lens L12 with a convex shape on the object side are cemented is used as an anti-shake group, and the image is shifted by moving the anti-shake group in a direction substantially perpendicular to the optical axis to perform image blur correction. Note that the biconcave lens L11 is the above-mentioned lens Lvcn, and the positive meniscus lens L12 is the above-mentioned lens Lvcp. Also, the object-side surface of the biconcave lens L11 has an aspherical shape such that its refractive power is weaker than the refractive power obtained from its paraxial curvature.

[0221] (2) Numerical examples Next, numerical examples applying specific numerical values of the zoom lens will be described. Table 19 shows the surface data of the zoom lens, and Table 20 shows the specification table of the zoom lens. Note that the 36th and 37th surfaces in Table 19 are the surface data of the cover glass CG.

[0222] Table 21 shows the variable interval on the optical axis of the zoom lens during zooming, and Table 22 shows the variable interval on the optical axis of the zoom lens during focusing. Note that Table 22 shows the values when the shooting distance (imaging distance) is 380.00 mm, 400.00 mm, and 400.00 mm at the wide-angle end, the intermediate focal length state, and the telephoto end, respectively. These shooting distances are the shortest imaging distances at each focal length.

[0223] Table 23 shows the focal lengths of the lens groups that make up the zoom lens. Table 24 shows the aspherical coefficients of the aspherical surfaces. Also, Table 25 shows the values of the respective conditional expressions (1) to (18).

[0224] Further, FIGS. 14 to 16 respectively show the longitudinal aberration diagrams at infinity focus at the wide-angle end, intermediate focal length state, and telephoto end of the zoom lens of Example 4.

[0225] Furthermore, the back focus at infinity focus at the wide-angle end of the zoom lens is as follows. fb = 39.437 (mm)

[0226] [Table 19] Surface number r d Nd vd H 1 234.7666 1.300 2.00069 25.46 31.000 2 138.4148 5.791 1.59282 68.62 30.558 3 -680.0462 0.200 30.302 4 69.5724 5.230 1.59282 68.62 28.400 5 161.1477 D5 27.926 6 ASP 79.5439 1.400 1.86791 41.50 18.481 7 16.1943 8.900 13.716 8 -318.2547 0.800 1.87450 36.30 13.541 9 45.1827 0.309 13.327 10 51.2199 8.660 1.73426 26.35 13.336 11 -25.6352 0.451 13.228 12 ASP -20.9608 1.200 1.77115 48.40 13.152 13 ASP -64.5265 D13 13.100 14 S 0.0000 1.200 8.750 15 53.1982 3.548 1.69350 53.18 12.260 16 ASP -79.4200 1.520 12.346 17 -266.2503 0.800 1.82595 41.71 12.461 18 88.0772 4.260 1.59282 68.62 12.571 19 -42.6289 0.624 12.691 20 ASP -78.1987 0.900 1.74974 49.75 12.900 21 60.1253 2.368 1.84666 23.78 12.727 22 185.3061 D22 12.759 23 47.5209 5.193 1.68881 54.43 13.170 24 -55.0964 0.200 13.066 25 -327.0636 0.800 1.96229 29.86 12.625 26 22.8885 6.220 1.49700 81.61 12.075 27 -77.0078 0.350 12.125 28 73.7860 5.020 1.61800 63.39 12.044 29 -73.2609 D29 11.750 30 -207.6716 2.500 1.80809 22.76 9.380 31 -36.7222 0.900 1.69350 53.18 9.429 32 ASP 22.1640 D32 9.493 33 52.7180 6.495 1.59282 68.62 15.993 34 -73.2205 0.800 1.69206 30.32 16.171 35 -416.6667 37.118 16.374 36 0.0000 2.000 1.51680 64.20 21.005 37 0.0000 1.000 21.342

[0227] [Table 20] f 24.839 59.958 102.474 Fno 4.121 4.119 4.120 ω 41.981 18.973 11.267 Y 21.633 21.633 21.633 TL 169.752 174.603 207.241

[0228] [Table 21] f 24.839 59.958 102.474 Shooting distance INF INF INF D5 1.000 20.275 53.597 D13 38.216 6.180 1.360 D22 4.143 3.278 2.700 D29 1.179 12.168 13.313 D32 7.156 14.643 18.212

[0229] [Table 22] Shooting distance 380.000 400.000 400.000 D29 1.849 15.198 20.630 D32 6.486 11.613 10.895

[0230] [Table 23] Group Frame number Focal length G1 1-5 140.430 G2 6-13 -21.836 G3 14-22 56.376 G4 23-29 39.322 G5 30-32 -31.033 G6 33-37 86.738

[0231] [Table 24] Surface numbers Κ A4 A6 A8 A10 A12 6 0 -3.5121E-07 1.2475E-09 -1.8924E-11 2.0318E-14 -9.3027E-18 12 0 3.4527E-05 -2.8731E-07 2.1583E-09 -7.5699E-12 1.1133E-14 13 0 1.8666E-05 -3.0289E-07 2.0678E-09 -7.5735E-12 1.0314E-14 16 0 1.3999E-05 -4.6523E-09 4.5363E-11 -3.1634E-13 9.7102E-16 20 0 2.6081E-06 -9.1362E-09 6.1882E-11 -2.3937E-13 3.9842E-16 32 0 -4.4734E-06 3.3579E-09 -4.8480E-10 4.0227E-12 -1.3728E-14

[0232] [Table 25] Example 1 Example 2 Example 3 Example 4 Conditional expression (1) Cr1f / fw 6.677 35.830 12.572 9.452 Conditional expression (2) (-ffw+Dfrw) / FBw 1.714 1.901 1.422 1.703 Conditional expression (3) 1 / |(1 / νdLvcn)-(1 / νdLvcp)| 46.591 37.770 24.364 45.555 Conditional expression (4) |(1-βvct)×βvctr| 1.194 4.004 1.682 1.198 Conditional expression (5) (Crff+Crfr) / (Crff-Crfr) 0.713 0.191 0.717 0.807 Conditional expression (6) |{1-(βft 2 )}×βftr 2 | 5.419 4.437 5.061 4.609 Conditional expression (6-1) |βft| 3.756 5.520 5.034 4.451 Conditional expression (7) |fw×tanωw| / (fsr - FBw) -0.197 -0.141 -0.029 -0.017 Conditional expression (8) NdLrn 1.971 1.847 2.001 1.962 Conditional expression (9) ΔPgF 0.000 0.014 0.004 0.000 Conditional expression (9 - 1) ΔPgFp 0.038 0.038 0.019 0.038 Conditional expression (10) fn / fw -0.861 -1.544 -0.815 -0.879 Conditional expression (11) ff / ft -0.307 -0.426 -0.416 -0.303 Conditional expression (12) νdLn 53.186 46.503 67.023 53.186 Conditional expression (13) |X1| / ft 0.369 0.260 0.525 0.366 Conditional expression (14) Crrf / ft 0.433 0.516 0.329 0.519 Conditional expression (15) ffft / ft 0.414 0.467 0.435 0.454 Conditional expression (16) Drfrt / ft 0.186 0.140 0.199 0.178 Conditional expression (17) fw / ffw -0.920 -0.648 -0.900 -0.895 Conditional expression (18) νdLp 22.761 23.785 17.980 22.761

Industrial Applicability

[0233] According to the present invention, it is possible to provide a standard zoom lens with high optical performance and an imaging device equipped with the zoom lens while reducing the weight of the focus group and the anti - shake group. In particular, the zoom lens is suitable for a zoom lens that includes a focal length of 50 mm in the zoom range in terms of 35 mm equivalent and has a half - angle of view (ω) at the wide - angle end larger than 24°.

Explanation of Reference Numerals

[0234] G1 ··· First lens group G2 ··· Second lens group G3 ··· Third lens group G4 ··· Fourth lens group G5 ··· Fifth lens group G6 ··· Sixth lens group F ··· Focus group S ··· Aperture stop CG ··· Cover glass IMG ··· Image plane

Claims

1. When the lens group arranged on the object side is defined as the front group with the widest air gap at the wide-angle end as the boundary, and the lens group arranged on the image side is defined as the rear group, the front group has a negative refractive power as a whole, the rear group has a positive refractive power as a whole, and the zooming is performed from the wide-angle end to the telephoto end by changing the air gap between the lens groups so as to reduce at least the air gap between the front group and the rear group, a focus group arranged within the rear group and moving in the optical axis direction when focusing from infinity to a nearby object, an anti-vibration group arranged on the object side of the focus group and movable in a direction substantially perpendicular to the optical axis, including the rear group has a lens Lrn having a negative refractive power of at least one sheet on the object side of the focus group, the focus group has a lens Ln having a negative refractive power of at least one sheet, A zoom lens characterized by satisfying the following conditions. (1) 4.50 < Cr1f / fw (6) 2.00 < |{1 - (βft × βft)} × βftr × βftr| < 15.00 (8) 1.971 ≦ NdLrn < 2.10 (11) -0.45 < ff / ft < -0.05 (12) 51.0 < νdLn < 98.0 (14) 0.01 < Crrf / ft ≦ 0.433 However, Cr1f: Radius of curvature of the most object-side surface of the zoom lens fw: Focal length of the zoom lens at the wide-angle end βft: Lateral magnification at infinite focus of the focus group at the telephoto end βftr: Combined lateral magnification at infinite focus of all lenses arranged on the image side of the focus group at the telephoto end NdLrn: Refractive index of the lens Lrn at the d line ff: Focal length of the focus group νdLn: Abbe number of the lens Ln at the d line Crrf: Radius of curvature of the most object-side surface of the rear group ft: Focal length of the zoom lens at the telephoto end

2. When the lens group arranged on the object side is defined as the front group with the widest air gap at the wide-angle end as the boundary, and the lens group arranged on the image side is defined as the rear group, having a diaphragm in the optical system, the front group has a negative refractive power as a whole, the rear group has a positive refractive power as a whole, and the zooming is performed from the wide-angle end to the telephoto end by changing the air gap between the lens groups so as to reduce at least the air gap between the front group and the rear group, when the lens group arranged most on the object side in the front group is defined as the first lens group, the first lens group moves in the optical axis direction when zooming from the wide-angle end to the telephoto end, A focus group disposed within the rear group and moving in the optical axis direction when focusing from infinity to a close object; An anti-shake group disposed closer to the object side than the focus group and movable in a direction substantially perpendicular to the optical axis; comprising the anti-shake group is disposed on the image side of the aperture stop; the rear group has a lens Lrn having at least one negative refractive power on the object side of the focus group; the focus group has a lens Ln having at least one negative refractive power; A zoom lens characterized by satisfying the following conditions. (1) 4.20 < Cr1f / fw (4-1) 0.50 < |(1 - βvct) × βvctr| < 2.3 (6) 2.00 < |{1 - (βft × βft)} × βftr × βftr| ≦ 5.419 (8) 1.84 < NdLrn < 2.10 (12) 51.0 < νdLn < 98.0 (13) 0.01 < |X1| / ft < 0.48 (14) 0.01 < Crrf / ft ≦ 0.433 However, Cr1f: The radius of curvature of the most object-side surface of the zoom lens; fw: The focal length of the zoom lens at the wide-angle end; βft: The lateral magnification at infinity focus of the focus group at the telephoto end; βftr: The combined lateral magnification at infinity focus of all lenses disposed on the image side of the focus group at the telephoto end; NdLrn: The refractive index of the lens Lrn at the d-line; νdLn: The Abbe number of the lens Ln at the d-line; X1: The amount of movement when the first lens group moves from the most image-side position to the most object-side position where the first lens group can be located during zooming from the wide-angle end to the telephoto end; Crrf: The radius of curvature of the most object-side surface of the rear group; ft: The focal length of the zoom lens at the telephoto end; βvct: The lateral magnification at infinity focus of the anti-shake group at the telephoto end; βvctr: The combined lateral magnification at infinity focus of all lenses disposed on the image side of the anti-shake group at the telephoto end;

3. The anti-shake group has at least one aspherical surface, The zoom lens according to claim 1 or claim 2, wherein the aspherical surface has an aspherical shape in which the refractive power is weaker than the refractive power obtained from its paraxial curvature.

4. The zoom lens according to claim 1, satisfying the following conditions. (4) 0.50 < |(1 - βvct) × βvctr| < 6.00 However, βvct: The lateral magnification at infinity focus of the anti-shake group at the telephoto end; βvctr: The combined lateral magnification at infinity focus of all lenses disposed on the image side of the anti-shake group at the telephoto end;

5. The anti-vibration group is a zoom lens according to any one of claims 1 to 4 included in the rear group.

6. The anti-vibration group is a zoom lens according to any one of claims 1 to 5, which is composed of one single lens unit.

7. A zoom lens according to any one of claims 1 to 6, satisfying the following conditions. (5) 0.00 < (Crff + Crfr) / (Crff - Crfr) < 5.00 However, Crff: The radius of curvature of the object-side surface of the focus group closest to the object. Crfr: The radius of curvature of the image-side surface of the focus group closest to the image.

8. The rear group has at least one lens on the image side of the focus group. The zoom lens according to any one of claims 1 to 7.

9. The rear group has at least one lens surface Sr with a negative refractive power on the image side of the focus group, and satisfies the following conditional formula. The zoom lens according to claim 8. (7) -0.400 < |fw × tan ωw| / (fsr - FBw) < -0.002 However, ωw: The half angle of the outermost chief ray of the zoom lens at the wide-angle end. fsr: The focal length of the lens surface Sr. FBw: The air-equivalent length from the image-side surface of the zoom lens closest to the image to the imaging surface at the wide-angle end.

10. The lens Lrn satisfies the following conditions. The zoom lens according to any one of claims 1 to 9. (9) -0.015 < ΔPgF < 0.022 However, ΔPgF: In a coordinate system with the partial dispersion ratio on the vertical axis and the Abbe number νd with respect to the d-line on the horizontal axis, the deviation from the reference line of the partial dispersion ratio when a straight line passing through the coordinates of the optical material C7 with a partial dispersion ratio of 0.5393 and νd of 60.49 and the coordinates of the optical material F2 with a partial dispersion ratio of 0.5829 and νd of 36.30 is used as the reference line.

11. The front group has at least one lens group with a negative refractive power. When the lens group with the largest negative refractive power in the front group is defined as the negative lens group n, the following conditions are satisfied. The zoom lens according to any one of claims 1 to 10. (10) -2.00 < fn / fw < -0.55 However, fn: The focal length of the negative lens group n.

12. The focus group has a negative refractive power. The zoom lens according to any one of claims 1 to 11.

13. When the lens surface closest to the focus group in the direction in which the focus group moves during focusing from infinity to a close object is defined as the lens surface Lnf, the zoom lens according to any one of claims 1 to 12, which satisfies the following conditions. (16) 0.015 < Drft / ft < 1.000 However, Drft: The distance on the optical axis at infinity focus between the focus group at the telephoto end and the lens surface Lnf

14. An imaging device comprising the zoom lens according to any one of claims 1 to 13, and an image sensor that converts an optical image formed by the zoom lens into an electrical signal on the image side of the zoom lens.

Images